Solvent kinetic isotope effects of human placental alkaline phosphatase in reverse micelles.

PubMed

Huang, T M; Hung, H C; Chang, T C; Chang, G G

1998-02-15

Human placental alkaline phosphatase was embedded in a reverse micellar system prepared by dissolving the surfactant sodium bis(2-ethylhexyl) sulphosuccinate (Aerosol-OT) in 2,2, 4-trimethylpentane. This microemulsion system provides a convenient instrumental tool to study the possible kinetic properties of the membranous enzyme in an immobilized form. The pL (pH/p2H) dependence of hydrolysis of 4-nitrophenyl phosphate has been examined over a pL range of 8.5-12.5 in both aqueous and reverse micellar systems. Profiles of log V versus pL were Ha-bell shaped in the acidic region but reached a plateau in the basic region in which two pKa values of 9.01-9.71 and 9.86-10.48, respectively, were observed in reverse micelles. However, only one pKa value of 9.78-10.27 in aqueous solution was detected. Profiles of log V/K versus pL were bell-shaped in the acidic region. However, they were wave-shaped in the basic region in which a residue of pKa 9.10-9.44 in aqueous solution and 8.07-8.78 in reverse micelles must be dehydronated for the reaction to reach an optimum. The V/K value shifted to a lower value upon dehydronation of a pKa value of 9.80-10.62 in aqueous solution and 11.23-12.17 in reverse micelles. Solvent kinetic isotope effects were measured at three pL values. At pL 9.5, the observed isotope effect was a product of equilibrium isotope effect and a kinetic isotope effect; at pL 10.4, the log V/K value was identical in water and deuterium. The deuterium kinetic isotope effect on V/K was 1.14 in an aqueous solution and 1.16 in reverse micelles. At pL 11.0 at which the log V values reached a plateau in either solvent system, the deuterium kinetic isotope effect on V was 2.08 in an aqueous solution and 0.62 in reverse micelles. Results from a proton inventory experiment suggested that a hydron transfer step is involved in the transition state of the catalytic reaction. The isotopic fractionation factor (pi) for deuterium for the transition state (piT) increased when the pH of the solution was raised. At pL 11.0, the piT was 1.07 in reverse micelles, which corresponds to the inverse-isotope effect of the reaction in this solvent system. Normal viscosity effects on kcat and kcat/Km were observed in aqueous solution, corresponding to a diffusional controlled physical step as the rate-limiting step. We propose that the rate-limiting step of the hydrolytic reaction changes from phosphate releasing in aqueous solution to a covalent phosphorylation or dephosphorylation step in reverse micelles.

Micellar versus hydro-organic mobile phases for retention-hydrophobicity relationship studies with ionizable diuretics and an anionic surfactant.

PubMed

Ruiz-Angel, M J; Carda-Broch, S; García-Alvarez-Coque, M C; Berthod, A

2004-03-19

Logarithm of retention factors (log k) of a group of 14 ionizable diuretics were correlated with the molecular (log P o/w) and apparent (log P(app)) octanol-water partition coefficients. The compounds were chromatographed using aqueous-organic (reversed-phase liquid chromatography, RPLC) and micellar-organic mobile phases (micellar liquid chromatography, MLC) with the anionic surfactant sodium dodecyl sulfate (SDS), in the pH range 3-7, and a conventional octadecylsilane column. Acetonitrile was used as the organic modifier in both modes. The quality of the correlations obtained for log P(app) at varying ionization degree confirms that this correction is required in the aqueous-organic mixtures. The correlation is less improved with SDS micellar media because the acid-base equilibriums are shifted towards higher pH values for acidic compounds. In micellar chromatography, an electrostatic interaction with charged solutes is added to hydrophobic forces; consequently, different correlations should be established for neutral and acidic compounds, and for basic compounds. Correlations between log k and the isocratic descriptors log k(w), log k(wm) (extrapolated retention to pure water in the aqueous-organic and micellar-organic systems, respectively), and psi0 (extrapolated mobile phase composition giving a k = 1 retention factor or twice the dead time), and between these descriptors and log P(app) were also satisfactory, although poorer than those between log k and log P(app) due to the extrapolation. The study shows that, in the particular case of the ionizable diuretics studied, classical RPLC gives better results than MLC with SDS in the retention hydrophobicity correlations.

Structural and phase transition changes of sodium dodecyl sulfate micellar solution in alcohols probed by small-angle neutron scattering (SANS)

NASA Astrophysics Data System (ADS)

Putra, Edy Giri Rachman; Patriati, Arum

2015-04-01

Small-angle neutron scattering (SANS) measurements on 0.3M sodium dodecyl sulfate (SDS) micellar solutions have been performed in the presence of n-alcohols, from ethanol to decanol at different alcohol concentrations, 2-10 wt%. The ellipsoid micellar structure which occurred in the 0.3M SDS in aqueous solution with the size range of 30-50 Å has different behavior at various hydrocarbon chain length and concentration of alcohols. At low concentration and short chain-length of alcohols, such as ethanol, propanol, and butanol, the size of micelles reduced and had a spherical-like structure. The opposite effect occurred as medium to long chain alcohols, such as hexanol, octanol and decanol was added into the 0.3M SDS micellar solutions. The micelles structure changed to be more elongated in major axis and then crossed the critical phase transition from micellar solution into liquid crystal phase as lamellar structure emerged by further addition of alcohols. The inter-lamellar distances were also depending on the hydrocarbon chain length and concentration of alcohols. In the meantime, the persistent micellar structures occurred in addition of medium chain of n-alcohol, pentanol at all concentrations.

Structural and phase transition changes of sodium dodecyl sulfate micellar solution in alcohols probed by small-angle neutron scattering (SANS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putra, Edy Giri Rachman; Patriati, Arum; Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Gadjah Mada, Bulaksumur, Yogyakarta 55281, Indonesia giri@batan.go.id

2015-04-16

Small-angle neutron scattering (SANS) measurements on 0.3M sodium dodecyl sulfate (SDS) micellar solutions have been performed in the presence of n-alcohols, from ethanol to decanol at different alcohol concentrations, 2–10 wt%. The ellipsoid micellar structure which occurred in the 0.3M SDS in aqueous solution with the size range of 30–50 Å has different behavior at various hydrocarbon chain length and concentration of alcohols. At low concentration and short chain-length of alcohols, such as ethanol, propanol, and butanol, the size of micelles reduced and had a spherical-like structure. The opposite effect occurred as medium to long chain alcohols, such as hexanol,more » octanol and decanol was added into the 0.3M SDS micellar solutions. The micelles structure changed to be more elongated in major axis and then crossed the critical phase transition from micellar solution into liquid crystal phase as lamellar structure emerged by further addition of alcohols. The inter-lamellar distances were also depending on the hydrocarbon chain length and concentration of alcohols. In the meantime, the persistent micellar structures occurred in addition of medium chain of n-alcohol, pentanol at all concentrations.« less

Effect of micellar collisions and polyvinylpyrrolidone confinement on the electrical conductivity percolation parameters of water/AOT/isooctane reverse micelles

NASA Astrophysics Data System (ADS)

Guettari, Moez; Aferni, Ahmed E. L.; Tajouri, Tahar

2017-12-01

The main aim of this paper is the analysis of micellar collisions and polymer confinement effects on the electrical conductivity percolative behavior of water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles. Firstly, we have performed conductance measurements of the system for three AOT to isooctane volume ratio, φm = 0.1 , 0.15 and 0.2 to examine the influence of micellar collisions on the percolation parameters. All the measurements were carried out over the 298.15 K-333.15 K temperature range at a fixed water to AOT molar ratio, W0 = 45 . We have assessed that the rise of micellar collisions frequency enhances the conductance percolation. Secondly, the confinement effect of a water-soluble polymer, polyvinylpyrrolidone (PVP), on the reverse micelles conductance behavior was investigated. Temperature-induced percolation, Tp , have shown a dependence on the polymer concentration, CPVP . It was also observed that for various PVP concentrations, the activation energy of percolation decreases. Finally, the values of the critical exponents determined in the presence and absence of PVP prove that the polymer affects the dynamic of percolation.

Identification of the active protein in rice bran protein having an inhibitory activity of cholesterol micellar solubility.

PubMed

Wang, Jilite; Shimada, Masaya; Nagaoka, Satoshi

2017-06-01

In our previous study, rice bran protein (RBP) inhibited cholesterol micellar solubility in vitro and decreased serum cholesterol level in rats. In the present study, RBP was separated and purified by size-exclusion chromatography and reversed-phase chromatography. The active protein of RBP related to cholesterol micellar solubility was identified as lectin and non-specific lipid-transfer protein 1 using MALDI-TOF mass spectrometry analysis.

Development of a Singlet Oxygen Absorption Capacity (SOAC) Assay Method. Measurements of the SOAC Values for Carotenoids and α-Tocopherol in an Aqueous Triton X-100 Micellar Solution.

PubMed

Mukai, Kazuo; Ouchi, Aya; Azuma, Nagao; Takahashi, Shingo; Aizawa, Koichi; Nagaoka, Shin-Ichi

2017-02-01

Recently, a new assay method for the quantification of the singlet oxygen absorption capacity (SOAC) of antioxidants (AOs) and food extracts in homogeneous organic solvents was proposed. In this study, second-order rate constants (k Q ) for the reaction of singlet oxygen ( 1 O 2 ) with eight different carotenoids (Cars) and α-tocopherol (α-Toc) were measured in an aqueous Triton X-100 (5.0 wt %) micellar solution (pH 7.4, 35 °C), which was used as a simple model of biomembranes. The k Q and relative SOAC values were measured using ultraviolet-visible (UV-vis) spectroscopy. The UV-vis absorption spectra of Cars and α-Toc were measured in both a micellar solution and chloroform, to investigate the effect of solvent on the k Q and SOAC values. Furthermore, decay rates (k d ) of 1 O 2 were measured in 0.0, 1.0, 3.0, and 5.0 wt % micellar solutions (pH 7.4), using time-resolved near-infrared fluorescence spectroscopy, to determine the absolute k Q values of the AOs. The results obtained demonstrate that the k Q values of AOs in homogeneous and heterogeneous solutions vary notably depending on (i) the polarity [dielectric constant (ε)] of the reaction field between AOs and 1 O 2 , (ii) the local concentration of AOs, and (iii) the mobility of AOs in solution. In addition, the k Q and relative SOAC values obtained for the Cars in a heterogeneous micellar solution differ remarkably from those in homogeneous organic solvents. Measurements of k Q and SOAC values in a micellar solution may be useful for evaluating the 1 O 2 quenching activity of AOs in biological systems.

Probes for the micellar cage effect. The magnetic 13c-isotope effect and a new cage product in the photolysis of dibenzyl ketone

NASA Astrophysics Data System (ADS)

Kraeutler, Bernhard; Turro, Nicholas J.

1980-03-01

An isotopic enrichment factor, α, is employed as a novel probe to study the effect of solute and of detergent concentration on micellar parameters. The formation of a new cage product is also found to follow monotonically the concentration of micelles in aqueous detergent solutions. It is shown by these probes that the average occupancy of the micelles by the solute does not significantly alter the dynamic micellar behavior with respect to reactions that occur in the micelle cage.

Block Copolymer Micelles for Photonic Fluids and Crystals.

PubMed

Poutanen, Mikko; Guidetti, Giulia; Gröschel, Tina I; Borisov, Oleg V; Vignolini, Silvia; Ikkala, Olli; Gröschel, Andre H

2018-04-24

Block copolymer micelles (BCMs) are self-assembled nanoparticles in solution with a collapsed core and a brush-like stabilizing corona typically in the size range of tens of nanometers. Despite being widely studied in various fields of science and technology, their ability to form structural colors at visible wavelength has not received attention, mainly due to the stringent length requirements of photonic lattices. Here, we describe the precision assembly of BCMs with superstretched corona, yet with narrow size distribution to qualify as building blocks for tunable and reversible micellar photonic fluids (MPFs) and micellar photonic crystals (MPCs). The BCMs form free-flowing MPFs with an average interparticle distance of 150-300 nm as defined by electrosteric repulsion arising from the highly charged and stretched corona. Under quiescent conditions, millimeter-sized MPCs with classical FCC lattice grow within the photonic fluid-medium upon refinement of the positional order of the BCMs. We discuss the generic properties of MPCs with special emphasis on surprisingly narrow reflected wavelengths with full width at half-maximum (fwhm) as small as 1 nm. We expect this concept to open a generic and facile way for self-assembled tunable micellar photonic structures.

Synergistic Growth of Giant Wormlike Micelles in Ternary Mixed Surfactant Solutions: Effect of Octanoic Acid.

PubMed

Georgieva, Gergana S; Anachkov, Svetoslav E; Lieberwirth, Ingo; Koynov, Kaloian; Kralchevsky, Peter A

2016-12-06

The synergistic growth of giant wormlike micelles in ternary mixed solutions composed of an anionic surfactant (sodium laurylethersulfate, SLES), a zwitterionic surfactant (cocamidopropyl betaine, CAPB), and octanoic acid (HC8) is studied. Rheological data and their analysis in terms of Cole-Cole plots and micellar characteristic times are presented, and the micellar structures behind the observed rheological behavior are revealed by cryo-TEM micrographs. The surfactant composition is fixed near the maximal micelle size of the binary SLES + CAPB system, whereas the concentration of HC8 is varied. At a given HC8 concentration, the viscosity of the ternary micellar solutions exhibits a very high and sharp peak. Polarized-light optical microscopy indicates that all investigated solutions are isotropic rather than liquid-crystalline. The cryo-TEM imaging shows complex phase behavior: wormlike micelles to the left of the peak, giant entangled wormlike micelles at the peak, and long wormlike micelles coexisting with multiconnected micellar aggregates to the right of the peak. The formation of multiconnected micelles leads to a drop in viscosity at the higher concentrations. The results contribute to a better understanding of the structure-rheology relations in micellar surfactant solutions and could be useful for controlling the properties of formulations in personal-care and house-hold detergency.

Complementary experimental-simulational study of surfactant micellar phase in the extraction process of metallic ions: Effects of temperature and salt concentration

NASA Astrophysics Data System (ADS)

Soto-Ángeles, Alan Gustavo; Rodríguez-Hidalgo, María del Rosario; Soto-Figueroa, César; Vicente, Luis

2018-02-01

The thermoresponsive micellar phase behaviour that exhibits the Triton-X-100 micelles by temperature effect and addition of salt in the extraction process of metallic ions was explored from mesoscopic and experimental points. In the theoretical study, we analyse the formation of Triton-X-100 micelles, load and stabilization of dithizone molecules and metallic ions extraction inside the micellar core at room temperature; finally, a thermal analysis is presented. In the experimental study, the spectrophotometric outcomes confirm the solubility of the copper-dithizone complex in the micellar core, as well as the extraction of metallic ions of aqueous environment via a cloud-point at 332.2 K. The micellar solutions with salt present a low absorbance value compared with the micellar solutions without salt. The decrease in the absorbance value is attributed to a change in the size of hydrophobic region of colloidal micelles. All transitory stages of extraction process are discussed and analysed in this document.

Self-Propulsion of Pure Water Droplets by Spontaneous Marangoni-Stress-Driven Motion

NASA Astrophysics Data System (ADS)

Izri, Ziane; van der Linden, Marjolein N.; Michelin, Sébastien; Dauchot, Olivier

2014-12-01

We report spontaneous motion in a fully biocompatible system consisting of pure water droplets in an oil-surfactant medium of squalane and monoolein. Water from the droplet is solubilized by the reverse micellar solution, creating a concentration gradient of swollen reverse micelles around each droplet. The strong advection and weak diffusion conditions allow for the first experimental realization of spontaneous motion in a system of isotropic particles at sufficiently large Péclet number according to a straightforward generalization of a recently proposed mechanism [S. Michelin, E. Lauga, and D. Bartolo, Phys. Fluids 25, 061701 (2013); S. Michelin and E. Lauga, J. Fluid Mech. 747, 572 (2014)]. Experiments with a highly concentrated solution of salt instead of water, and tetradecane instead of squalane, confirm the above mechanism. The present swimming droplets are able to carry external bodies such as large colloids, salt crystals, and even cells.

Self-propulsion of pure water droplets by spontaneous Marangoni-stress-driven motion.

PubMed

Izri, Ziane; van der Linden, Marjolein N; Michelin, Sébastien; Dauchot, Olivier

2014-12-12

We report spontaneous motion in a fully biocompatible system consisting of pure water droplets in an oil-surfactant medium of squalane and monoolein. Water from the droplet is solubilized by the reverse micellar solution, creating a concentration gradient of swollen reverse micelles around each droplet. The strong advection and weak diffusion conditions allow for the first experimental realization of spontaneous motion in a system of isotropic particles at sufficiently large Péclet number according to a straightforward generalization of a recently proposed mechanism [S. Michelin, E. Lauga, and D. Bartolo, Phys. Fluids 25, 061701 (2013); S. Michelin and E. Lauga, J. Fluid Mech. 747, 572 (2014)]. Experiments with a highly concentrated solution of salt instead of water, and tetradecane instead of squalane, confirm the above mechanism. The present swimming droplets are able to carry external bodies such as large colloids, salt crystals, and even cells.

Flow of viscoelastic fluids around a sharp microfluidic bend: Role of wormlike micellar structure

NASA Astrophysics Data System (ADS)

Hwang, Margaret Y.; Mohammadigoushki, Hadi; Muller, Susan J.

2017-04-01

We examine the flow and instabilities of three viscoelastic fluids—a semidilute aqueous solution of polyethylene oxide (PEO) and two wormlike micellar solutions of cetylpyridinium chloride and sodium salicylate—around a microfluidic 90∘ bend, in which shear deformation and streamline curvature dominate. Similar to results reported by Gulati et al. [S. Gulati et al., Phys. Rev. E 78, 036314 (2008), 10.1103/PhysRevE.78.036314; S. Gulati et al., J. Rheol. 54, 375 (2010), 10.1122/1.3308643] for PEO solutions, we report a critical Weissenberg number (Wi) for the onset of lip vortex formation upstream of the corner. However, the decreased aspect ratio (channel depth to width) results in a slightly higher critical Wi and a vortex that grows more slowly. We consider wormlike micellar solutions of two salt to surfactant concentration ratios R =0.55 and R =0.79 . At R =0.55 , the wormlike micelles are linear and exhibit strong viscoelastic behavior, but at R =0.79 , the wormlike micelles become branched and exhibit shear-banding behavior. Microfluidic experiments on the R =0.55 solution reveal two flow transitions. The first transition, at Wi =6 , is characterized by the formation of a stationary lip vortex upstream of the bend; at the second transition, at Wi =20 , the vortex fluctuates in time and changes size. The R =0.79 solution also exhibits two transitions. The first transition at Wi =4 is characterized by the appearance of two intermittent vortices, one at the lip and one at the far outside corner. Increasing the flow rate to Wi >160 results in a transition to a second unstable regime, where there is only a lip vortex that fluctuates in size. The difference in flow transitions in PEO and wormlike micellar solutions presumably arises from the additional contribution of wormlike micellar breakage and reformation under shear. The flow transitions in wormlike micellar solutions are also significantly affected by chain branching.

Micellar Packing in Aqueous Solutions of As-Received and Pure Pluronic Block Copolymers

NASA Astrophysics Data System (ADS)

Ryu, Chang; Park, Han Jin

2013-03-01

Pluronic block copolymers (Pluronics) are produced on a commercial scale to enable wide range of novel applications from emulsification and colloidal stabilization as nonionic surfactants. While the Pluronic block copolymers offer the advantages of being readily available for such applications, it contains non-micellizable low molecular weight (MW) impurities that would interfere with the self-assembly and micellar packing of PEO-PPO-PEO triblock copolymers in aqueous solutions. The impacts of the low MW impurities will be discussed on the micellar packing of Pluronics F108 and F127 solutions, which form BCC and FCC. While as-received Pluronic samples typically contain about 20 wt.% low MW impurities, we were able to reduce the impurity level to less than 2 wt.% using our large scale purification technique. Comparative studies on small angle x-ray scattering (SAXS) experiments on as-received and purified Pluronics solutions revealed that the contents of triblock copolymers in solutions essentially governs the inter-micellar distance of Pluronic cubic structures. A universal relationship between triblock copolymer concentration and SAXS-based domain spacing has been finally discussed. Funding from Agency for Defense Development, Korea.

Self-assembly of water-soluble nanocrystals

DOEpatents

Fan, Hongyou [Albuquerque, NM; Brinker, C Jeffrey [Albuquerque, NM; Lopez, Gabriel P [Albuquerque, NM

2012-01-10

A method for forming an ordered array of nanocrystals where a hydrophobic precursor solution with a hydrophobic core material in an organic solvent is added to a solution of a surfactant in water, followed by removal of a least a portion of the organic solvent to form a micellar solution of nanocrystals. A precursor co-assembling material, generally water-soluble, that can co-assemble with individual micelles formed in the micellar solution of nanocrystals can be added to this micellar solution under specified reaction conditions (for example, pH conditions) to form an ordered-array mesophase material. For example, basic conditions are used to precipitate an ordered nanocrystal/silica array material in bulk form and acidic conditions are used to form an ordered nanocrystal/silica array material as a thin film.

Fabrication of size-controlled nanoring arrays by selective incorporation of ionic liquids in diblock copolymer micellar cores

NASA Astrophysics Data System (ADS)

Kim, Sung-Soo; Kang, Donghwi; Sohn, Byeong-Hyeok

2017-06-01

We report the synthesis of arrayed nanorings with tunable physical dimensions from thin films of polystyrene-block-poly(4-vinylpyridine) (PS-P4VP) micelles. For accurate control of the inner and outer diameters of the nanorings, we added imidazolium-based ionic liquids (ILs) into the micellar solution, which were eventually incorporated into the micellar cores. We observed the structural changes of the micellar cores coated on a substrate due to the presence of ILs. The spin-coated micellar cores were treated with an acidic precursor solution and generated toroid nanostructures, of which size depended on the amount of IL loaded into the micelles. We then treated the transformed micellar films with oxygen plasma to produce arrays of various metal and oxide nanorings on a substrate. The spacings and diameters of nanorings were governed by the molecular weight of the PS-P4VP and the amount of IL used. We also demonstrated that arrayed Pt nanorings enabled the fabrication of reduced graphene oxide anti-nanoring arrays via a catalytic tailoring process.

Engineering cocrystal solubility, stability, and pH(max) by micellar solubilization.

PubMed

Huang, Neal; Rodríguez-Hornedo, Naír

2011-12-01

Cocrystals offer great promise in enhancing drug aqueous solubilities, but face the challenge of conversion to a less soluble drug when in contact with solvent. This manuscript shows that differential solubilization of cocrystal components by micelles can impart thermodynamic stability to otherwise unstable cocrystals. The theoretical foundation for controlling cocrystal solubility and stability is presented by considering the contributions of micellar solubilization and ionization of cocrystal components. A surfactant critical stabilization concentration (CSC) and a solution pH (pH(max)) where cocrystal and drug are thermodynamically stable are shown to characterize cocrystal stability in micellar solutions. The solubility, CSC, and pH(max) of carbamazepine cocrystals in micellar solutions of sodium lauryl sulfate predicted by the models are in very good agreement with experimental measurements. The findings from this work demonstrate that cocrystal CSC and pH(max) can be tailored from the selection of coformer and solubilizing additives such as surfactants, thus providing an unprecedented level of control over cocrystal stability and solubility via solution phase chemistry. Copyright © 2011 Wiley-Liss, Inc.

Simulating the injection of micellar solutions to recover diesel in a sand column.

PubMed

Bernardez, Letícia A; Therrien, René; Lefebvre, René; Martel, Richard

2009-01-26

This paper presents numerical simulations of laboratory experiments where diesel, initially present at 18% residual saturation in a sand column, was recovered by injecting a micellar solution containing the surfactant Hostapur SAS-60 (SAS), and two alcohols, n-butanol (n-BuOH), and n-pentanol (n-PeOH). The micellar solution was developed and optimized for diesel recovery using phase diagrams and soil column experiments. Numerical simulations with the compositional simulator UTCHEM agree with the experimental results and show that the entire residual diesel in the sand column was recovered after the downward injection of 5 pore volumes of the micellar solution. Recovery of diesel occurs by enhanced solubility in the microemulsion phase and by mobilization. An additional series of simulations investigated the effects of phase transfer, alcohol partitioning, and component segregation on diesel recovery. These simulations indicate that diesel can be accurately represented in the model by a single component, but that the pseudo-component approach for active matter and the assumption of local phase equilibrium leads to an underestimation of diesel mobilization.

Simulating the injection of micellar solutions to recover diesel in a sand column

NASA Astrophysics Data System (ADS)

Bernardez, Letícia A.; Therrien, René; Lefebvre, René; Martel, Richard

2009-01-01

This paper presents numerical simulations of laboratory experiments where diesel, initially present at 18% residual saturation in a sand column, was recovered by injecting a micellar solution containing the surfactant Hostapur SAS-60 (SAS), and two alcohols, n-butanol ( n-BuOH), and n-pentanol ( n-PeOH). The micellar solution was developed and optimized for diesel recovery using phase diagrams and soil column experiments. Numerical simulations with the compositional simulator UTCHEM agree with the experimental results and show that the entire residual diesel in the sand column was recovered after the downward injection of 5 pore volumes of the micellar solution. Recovery of diesel occurs by enhanced solubility in the microemulsion phase and by mobilization. An additional series of simulations investigated the effects of phase transfer, alcohol partitioning, and component segregation on diesel recovery. These simulations indicate that diesel can be accurately represented in the model by a single component, but that the pseudo-component approach for active matter and the assumption of local phase equilibrium leads to an underestimation of diesel mobilization.

Flow-induced gelation of living (micellar) polymers

NASA Technical Reports Server (NTRS)

Bruinsma, Robijn; Gelbart, William M.; Ben-Shaul, Avinoam

1992-01-01

The effect of shear velocity gradients on the size (L) of rodlike micelles in dilute and semidilute solution is considered. A kinetic equation is introduced for the time-dependent concentration of aggregates of length L, consisting of 'bimolecular' combination processes L + L-prime yield (L + L-prime) and unimolecular fragmentations L yield L + (L - L-prime). The former are described by a generalization (from spheres to rods) of the Smoluchowski mechanism for shear-induced coalesence of emulsions, and the latter by incorporating the tension-deformation effects due to flow. Steady-state solutions to the kinetic equation are obtained, with the corresponding mean micellar size evaluated as a function of the Peclet number P (i.e., the dimensionless ratio of the flow rate and the rotational diffusion coefficient). For sufficiently dilute solutions, only a weak dependence of the micellar size on P is found. In the semidilute regime, however, an apparent divergence in the micellar size at P of about 1 suggests a flow-induced first-order gelation phenomenon.

Dielectric relaxation spectroscopy shows a sparingly hydrated interface and low counterion mobility in triflate micelles.

PubMed

Lima, Filipe S; Chaimovich, Hernan; Cuccovia, Iolanda M; Buchner, Richard

2013-08-13

The properties of ionic micelles are affected by the nature of the counterion. Specific ion effects can be dramatic, inducing even shape and phase changes in micellar solutions, transitions apparently related to micellar hydration and counterion binding at the micellar interface. Thus, determining the hydration and dynamics of ions in micellar systems capable of undergoing such transitions is a crucial step in understanding shape and phase changes. For cationic micelles, such transitions are common with large organic anions as counterions. Interestingly, however, phase separation also occurs for dodecyltrimethylammonium triflate (DTATf) micelles in the presence of sodium triflate (NaTf). Specific ion effects for micellar solutions of dodecyltrimethylammonium chloride (DTAC), bromide (DTAB), methanesulfonate (DTAMs), and triflate (DTATf) were studied with dielectric relaxation spectroscopy (DRS), a technique capable of monitoring hydration and counterion dynamics of micellar aggregates. In comparison to DTAB, DTAC, and DTAMs, DTATf micelles were found to be considerably less hydrated and showed reduced counterion mobility at the micellar interface. The obtained DTATf and DTAMs data support the reported central role of the anion's -CF3 moiety with respect to the properties of DTATf micelles. The reduced hydration observed for DTATf micelles was rationalized in terms of the higher packing of this surfactant compared to that of other DTA-based systems. The decreased mobility of Tf(-) anions condensed at the DTATf interface strongly suggests the insertion of Tf(-) in the micellar interface, which is apparently driven by the strong hydrophobicity of -CF3.

Strip waves in vibrated shear-thickening wormlike micellar solutions

NASA Astrophysics Data System (ADS)

Epstein, T.; Deegan, R. D.

2010-06-01

We present an instability in vertically vibrated dilute wormlike micellar solutions. Above a critical driving acceleration the fluid forms elongated solitary domains of high amplitude waves. We model this instability using a Mathieu equation modified to account for the non-Newtonian character of the fluid. We find that our model successfully reproduces the observed transitions.

Phase separation in living micellar networks

NASA Astrophysics Data System (ADS)

Cristobal, G.; Rouch, J.; Curély, J.; Panizza, P.

We present a lattice model based on two n→0 spin vectors, capable of treating the thermodynamics of living networks in micellar solutions at any surfactant concentration. We establish an isomorphism between the coupling constants in the two spin vector Hamiltonian and the surfactant energies involved in the micellar situation. Solving this Hamiltonian in the mean-field approximation allows one to calculate osmotic pressure, aggregation number, free end and cross-link densities at any surfactant concentration. We derive a phase diagram, including changes in topology such as the transition between spheres and rods and between saturated and unsaturated networks. A phase separation can be found between a saturated network and a dilute solution composed of long flexible micelles or a saturated network and a solution of spherical micelles.

Nanoparticle Delivery Of RNAi Therapeutics For Ocular Vesicant Injury

DTIC Science & Technology

2014-12-01

micellar nanoparticles stabilized with disulfide crosslinking, hypothesizing that PEG corona on micellar nanoparticles could reduce toxicity while...micelles. This is analogous to micelle assembly, where the shape control is governed by the volume ratio of the hydrophilic ( corona ) to...self-assembly of the complexes between siRNA and LPEI-g-PEG copolymer carriers. The PEG corona and reversibly crosslinked core of the micelles enable

Study to determine the technical and economic feasibility of reclaiming chemicals used in micellar polymer and low tension surfactant flooding. Final report. [Ultrafiltration membranes and reverse osmosis membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stephens, R.H.; Himmelblau, A.; Donnelly, R.G.

1978-02-01

Energy Resources Company has developed a technology for use with enhanced oil recovery to achieve emulsion breaking and surfactant recovery. By using ultrafiltration membranes, the Energy Resources Company process can dewater an oil-in-water type emulsion expected from enhanced oil recovery projects to the point where the emulsion can be inverted and treated using conventional emulsion-treating equipment. By using a tight ultrafiltration membrane or a reverse osmosis membrane, the Energy Resources Company process is capable of recovering chemicals such as surfactants used in micellar polymer flooding.

Complexation of lysozyme with adsorbed PtBS-b-SCPI block polyelectrolyte micelles on silver surface.

PubMed

Papagiannopoulos, Aristeidis; Christoulaki, Anastasia; Spiliopoulos, Nikolaos; Vradis, Alexandros; Toprakcioglu, Chris; Pispas, Stergios

2015-01-20

We present a study of the interaction of the positively charged model protein lysozyme with the negatively charged amphiphilic diblock polyelectrolyte micelles of poly(tert-butylstyrene-b-sodium (sulfamate/carboxylate)isoprene) (PtBS-b-SCPI) on the silver/water interface. The adsorption kinetics are monitored by surface plasmon resonance, and the surface morphology is probed by atomic force microscopy. The micellar adsorption is described by stretched-exponential kinetics, and the micellar layer morphology shows that the micelles do not lose their integrity upon adsorption. The complexation of lysozyme with the adsorbed micellar layers depends on the micelles arrangement and density in the underlying layer, and lysozyme follows the local morphology of the underlying roughness. When the micellar adsorbed amount is small, the layers show low capacity in protein complexation and low resistance in loading. When the micellar adsorbed amount is high, the situation is reversed. The adsorbed layers both with or without added protein are found to be irreversibly adsorbed on the Ag surface.

Phosphatidylcholine embedded micellar systems: enhanced permeability through rat skin.

PubMed

Spernath, Aviram; Aserin, Abraham; Sintov, Amnon C; Garti, Nissim

2008-02-15

Micellar and microemulsion systems are excellent potential vehicles for delivery of drugs because of their high solubilization capacity and improved transmembrane bioavailability. Mixtures of propylene glycol (PG) and nonionic surfactants with sodium diclofenac (DFC) were prepared in the presence of phosphatidylcholine (PC) as transmembrane transport enhancers. Fully dilutable systems with maximum DFC solubilization capacity (SC) at pH 7 are presented. It was demonstrated that the concentrates underwent phase transitions from reverse micelles to swollen reverse micelles and, via the bicontinuous transitional mesophase, into inverted O/W microstructures. The SC decreases as a function of dilution. DFC transdermal penetration using rat skin in vitro correlated with SC, water content, effect of phospholipid content, presence of an oil phase, and ethanol. Skin penetration from the inverted bicontinuous mesophase and the skin penetration from the O/W-like microstructure were higher than that measured from the W/O-like droplets, especially when the micellar system containing the nonionic surfactant, sugar ester L-1695, and hexaglycerol laurate. PC embedded within the micelle interface significantly increased the penetration flux across the skin compared to micellar systems without the embedded PC at their interface. Moreover, the combination of PC with HECO40 improved the permeation rate (P) and shortened the lag-time (T(L)).

Vertical structures in vibrated wormlike micellar solutions

NASA Astrophysics Data System (ADS)

Epstein, Tamir; Deegan, Robert

2008-11-01

Vertically vibrated shear thickening particulate suspensions can support a free-standing interfaces oriented parallel to gravity. We find that shear thickening worm-like micellar solutions also support such vertical interfaces. Above a threshold in acceleration, the solution spontaneously accumulates into a labyrinthine pattern characterized by a well-defined vertical edge. The formation of vertical structures is of interest because they are unique to shear-thickening fluids, and they indicate the existence of an unknown stress bearing mechanism.

Rotational reorientation dynamics of Aerosol-OT reverse micelles formed in near-critical propane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heitz, M.P.; Bright, F.V.

1996-06-01

The rotational reorientation kinetics of two fluorescent solutes (rhodamine 6G, R6G, and rhodamine 101, R101) have been determined in sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT, AOT) reverse micelles formed in liquid and near-critical propane. We show that the amount of water loading ([water]/[AOT], R), continuous phase density, and temperature all influence the solute rotational dynamics. In all cases, the decay of anisotropy data (i.e., frequency-dependent differential polarized phase angle and polarized modulation ratio) are well described by a bi-exponential decay law. We find that the faster rotational correlation times are similar to but slightly less than the values predicted for an individualmore » AOT reverse micelle rotating in propane. The recovered rotational correlation times range from 200 to 500 ps depending on experimental conditions. This faster rotational process is explained in terms of lateral diffusion of the fluorophore along the water/headgroup interfacial region within the reverse micelle. The recovered values for the slower rotational correlation times range from 7 to 18 ns. These larger rotational reorientation times are assigned to varying micelle-micelle (i.e., tail-tail) interactions in the low-density, highly compressible fluid region. We also quantify the contribution of the reverse micellar {open_quotes}aggregate{close_quotes} to the total decay of anisotropy. {copyright} {ital 1996} {ital Society for Applied Spectroscopy}« less

SOLUBILIZATION OF DODECANE, TETRACHLOROETHYLENE, AND 1,2-DICHLOROBENZENE IN MICELLAR SOLUTIONS OF ETHOXYLATED NONIONIC SURFACTANTS

EPA Science Inventory

Although surfactants have received considerable attention as a potential means for enhancing the recovery of organic compounds from the subsurface, only limited information is available regarding the micellar solubilization of common groundwater contaminants by nonionic surfactan...

Evidence of modifications of micellar interface in sol-gel glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Catuara, C.M.; Lin, C.T.

1994-12-31

A new sol-gel procedure using micellar solutions has been developed to immobilize local anesthetic drugs in optically transparent glass. Dibucaine was selected as a direct emission probe at 77 K for determining the forms of the anesthetic drug (free base, monoprotonated, and/or diprotonated) and its location (hydrophobic core, interfacial layer or hydrophilic region) in micelles. The photophysical properties of local anesthetics obtained in gels are compared to those in solutions. During the gelation stage, the predominant drug species was identified as free base dibucaine embedded in the hydrophobic core of neutral as well as charged micelles. This observation suggests thatmore » the micellar interface was modified by the large hydrophilic gel surface during the gelation stage. The modified micellar interface allows an increase in the partition of free base dibucaine into the hydrophobic region. At the xerogel stage, however, the collapse of micellar structure provides a direct interaction of dibucaine with the acidic gel surface, leading to a formation of diprotonated dibucaine. The results are discussed in terms of molecular basis of pharmacological implications such as drug delivery, release, and transport under microencapsulation conditions.« less

Wetting properties and critical micellar concentration of benzalkonium chloride mixed in sodium hypochlorite.

PubMed

Bukiet, Frédéric; Couderc, Guillaume; Camps, Jean; Tassery, Hervé; Cuisinier, Frederic; About, Imad; Charrier, Anne; Candoni, Nadine

2012-11-01

The purposes of the present study were to (1) assess the effect of the addition of benzalkonium chloride to sodium hypochlorite on its wetting properties, contact angle, and surface energy; (2) determine the critical micellar concentration of benzalkonium chloride in sodium hypochlorite; and (3) investigate the influence of addition of benzalkonium chloride on the free chlorine level, cytotoxicity, and antiseptic properties of the mixture. Solutions of benzalkonium chloride, with concentrations ranging from 0%-1%, were mixed in 2.4% sodium hypochlorite and tested as follows. The wetting properties were investigated by measuring the contact angle of the solutions on a nondehydrated dentin surface by using the static sessile drop method. The pending drop technique was subsequently used to determine the surface energy of the solutions. The critical micellar concentration of benzalkonium chloride mixed in sodium hypochlorite was calculated from the data. When 2.4% NaOCl was mixed with benzalkonium chloride at the critical micellar concentration, 3 parameters were tested: free chloride content, cytotoxicity, and antibacterial effects against Enterococcus faecalis. The contact angle (P < .001) as well as the surface energy (P < .001) significantly decreased with increasing benzalkonium chloride concentrations. The critical micellar concentration of benzalkonium chloride in sodium hypochlorite was 0.008%. At this concentration, the addition of benzalkonium chloride had no effect on the free chlorine content, cytotoxicity, or antibacterial efficiency of the mixture. The addition of benzalkonium chloride to sodium hypochlorite at the critical micellar concentration reduced the contact angle by 51.2% and the surface energy by 53.4%, without affecting the free chloride content, cytotoxicity, or antibacterial properties of the mixture. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Optical absorption, electron spin resonance, and electron spin echo studies of the photoionization of tetramethylbenzidine in cationic and anionic synthetic vesicles: comparison with analogous micellar systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, A.S.W.; Kevan, L.

1983-09-07

The photoionization of N,N,N',N'-tetramethylbenzidine (TMB) in dihexadecylphosphate anionic vesicles and in dioctadecyldimethylammonium chloride cationic vesicles has been studied by optical absorption and electron spin resonance in liquid and frozen solutions. The TMB cation has been observed to be stabilized in both types of vesicles. The photoionization efficiency is about twofold greater in the cationic vesicles compared to the anionic vesicles. Shifts in the optical absorption maximum between micellar and vesicle solutions indicate that TMB is in a less polar environment in the vesicle systems. Electron spin echo modulation spectrometry has been used to detect TMB cation-water interactions that are foundmore » to be weaker than in previously studied micellar solutions. This is consistent with the optical absorption results and with an asymmetric solubilization site for TMB and TMB/sup +/ within the vesicular structure. A new absorption in the photoionized vesicles is assigned to a nonparamagnetic diamine-diimine charge-transfer complex between two TMB cations in the same vesicle. This complex is not formed in micellar systems. 5 figures.« less

Electron spin resonance and electron spin echo modulation of n-doxylstearic acid and N,N,N',N'-tetramethylbenzidine photoionization in sodium versus lithium dodecyl sulfate micellar solutions: effect of 15-crown-5 and 18-crown-6 ether addition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baglioni, P.; Rivara-Minten, E.; Kevan, L.

1988-08-11

Electron spin echo modulation and electron spin resonance spectra of photogenerated N,N,N',N'-tetramethylbenzidine (TMB) cation radical and n-doxylstearic acids (n-DSA) in frozen micellar solutions of sodium and lithium dodecyl sulfate containing 15-crown-5 and 18-crown-6 ethers in D/sub 2/O have been studied as a function of crown ether concentration. Modulation effects due to N-DSA with water deuteriums give direct evidence that both crown ethers are mainly located at the micellar interface and that this causes a decrease of the hydration of the micellar interface. Crown ether complexation constants for sodium and lithium micellar counterions are reported and show that 18-crown-6 > 15-crown-5more » for sodium counterion and 15-crown-5 > 18-crown-6 for lithium counterion. Modulation effects from TMB/sup +/ interaction with water deuteriums indicate that the TMB molecule moves toward the micelle interfacial region when sodium or lithium cations are complexed by crown ethers. The TMB/sup +/ yield upon TMB photoionization increases by about 10% with crown ether addition for SDS and LDS micellar systems, but it is greater if the absolute values for the LDS system are compared to those for the SDS micellar system. This behavior correlates with the strength of TMB/sup +/-water interactions and suggests that the main factor in the photoionization efficiency is the photocation-water interaction.« less

Self-assembly of block copolymer micelles: synthesis via reversible addition-fragmentation chain transfer polymerization and aqueous solution properties.

PubMed

Mya, Khine Y; Lin, Esther M J; Gudipati, Chakravarthy S; Gose, Halima B A S; He, Chaobin

2010-07-22

Poly(hexafluorobutyl methacrylate) (PHFBMA) homopolymer was synthesized by reversible addition-fragmentation chain transfer (RAFT)-mediated living radical polymerization in the presence of cyano-2-propyl dithiobenzoate (CPDB) RAFT agent. A block copolymer of PHFBMA-poly(propylene glycol acrylate) (PHFBMA-b-PPGA) with dangling poly(propylene glycol) (PPG) side chains was then synthesized by using CPDB-terminated PHFBMA as a macro-RAFT agent. The amphiphilic properties and self-assembly of PHFBMA-b-PPGA block copolymer in aqueous solution were investigated by dynamic and static light scattering (DLS and SLS) studies, in combination with fluorescence spectroscopy and transmission electron microscopy (TEM). Although PPG shows moderately hydrophilic character, the formation of nanosize polymeric micelles was confirmed by fluorescence and TEM studies. The low value of the critical aggregation concentration exhibited that the tendency for the formation of copolymer aggregates in aqueous solution was very high due to the strong hydrophobicity of the PHFBMA(145)-b-PPGA(33) block copolymer. The combination of DLS and SLS measurements revealed the existence of micellar aggregates in aqueous solution with an association number of approximately 40 +/- 7 for block copolymer micelles. It was also found in TEM observation that there are 40-50 micelles accumulated into one aggregate and these micelles are loosely packed inside the aggregate.

CO2-Reactive Ionic Liquid Surfactants for the Control of Colloidal Morphology.

PubMed

Brown, Paul; Sresht, Vishnu; Eral, Burak H; Fiore, Andrew; de la Fuente-Núñez, César; O'Mahony, Marcus; Mendes, Gabriel P; Heller, William T; Doyle, Patrick S; Blankschtein, Daniel; Hatton, T Alan

2017-08-08

This article reports on a new class of stimuli-responsive surfactant generated from commercially available amphiphiles such as dodecyltrimethylammmonium bromide (DTAB) by substitution of the halide counterion with counterions such as 2-cyanopyrrolide, 1,2,3-triazolide, and L-proline that complex reversibly with CO 2 . Through a combination of small-angle neutron scattering (SANS), electrical conductivity measurements, thermal gravimetric analysis, and molecular dynamics simulations, we show how small changes in charge reorganization and counterion shape and size induced by complexation with CO 2 allow for fine-tunability of surfactant properties. We then use these findings to demonstrate a range of potential practical uses, from manipulating microemulsion droplet morphology to controlling micellar and vesicular aggregation. In particular, we focus on the binding of these surfactants to DNA and the reversible compaction of surfactant-DNA complexes upon alternate bubbling of the solution with CO 2 and N 2 .

CO 2 -Reactive Ionic Liquid Surfactants for the Control of Colloidal Morphology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Paul; Sresht, Vishnu; Eral, Burak H.

Here, this article reports on a new class of stimuli-responsive surfactant generated from commercially available amphiphiles such as dodecyltrimethylammmonium bromide (DTAB) by substitution of the halide counterion with counterions such as 2-cyanopyrrolide, 1,2,3-triazolide, and L-proline that complex reversibly with CO 2. Through a combination of small-angle neutron scattering (SANS), electrical conductivity measurements, thermal gravimetric analysis, and molecular dynamics simulations, we show how small changes in charge reorganization and counterion shape and size induced by complexation with CO 2 allow for fine-tunability of surfactant properties. Additionally, we then use these findings to demonstrate a range of potential practical uses, from manipulatingmore » microemulsion droplet morphology to controlling micellar and vesicular aggregation. In particular, we focus on the binding of these surfactants to DNA and the reversible compaction of surfactant–DNA complexes upon alternate bubbling of the solution with CO 2 and N 2.« less

CO 2 -Reactive Ionic Liquid Surfactants for the Control of Colloidal Morphology

DOE PAGES

Brown, Paul; Sresht, Vishnu; Eral, Burak H.; ...

2017-07-12

Here, this article reports on a new class of stimuli-responsive surfactant generated from commercially available amphiphiles such as dodecyltrimethylammmonium bromide (DTAB) by substitution of the halide counterion with counterions such as 2-cyanopyrrolide, 1,2,3-triazolide, and L-proline that complex reversibly with CO 2. Through a combination of small-angle neutron scattering (SANS), electrical conductivity measurements, thermal gravimetric analysis, and molecular dynamics simulations, we show how small changes in charge reorganization and counterion shape and size induced by complexation with CO 2 allow for fine-tunability of surfactant properties. Additionally, we then use these findings to demonstrate a range of potential practical uses, from manipulatingmore » microemulsion droplet morphology to controlling micellar and vesicular aggregation. In particular, we focus on the binding of these surfactants to DNA and the reversible compaction of surfactant–DNA complexes upon alternate bubbling of the solution with CO 2 and N 2.« less

Spectral studies on the interaction of pinacyanol chloride with binary surfactants in aqueous medium.

PubMed

Manna, Kausik; Panda, Amiya Kumar

2009-12-01

Interaction of pinacyanol chloride (PIN) with pure and binary mixtures of cetyltrimethylammonium bromide (CTAB) and sodium deoxycholate (NaDC) was spectroscopically studied. Interaction of PIN with pure NaDC produced a blue shifted metachromatic band (at approximately 502 nm), which gradually shifted to higher wavelength region as the concentration of NaDC increased in the pre-micellar stage. For CTAB only intensity of both the bands increased without any shift. Mixed surfactant systems behaved differently than the pure components. Absorbance of monomeric band with a slight red-shift, and a simultaneous decrease in the absorbance of dimeric band of PIN, were observed for all the combinations in the post-micellar region. PIN-micelle binding constant (K(b)) for pure as well as mixed was determined from spectral data using Benesi-Hildebrand equation. Using the idea of Regular Solution Theory, micellar aggregates were assumed to be predominant than other aggregated state, like vesicles. Aggregation number was determined by fluorescence quenching method. Spectral analyses were also done to evaluate CMC values. Rubinigh's model for Regular Solution Theory was employed to evaluate the interaction parameters and micellar composition. Strong synergistic interaction between the oppositely charged surfactants was noted. Bulkier nature of NaDC lowered down its access in mixed micellar system.

Tuning Micellar Structures in Supercritical CO2 Using Surfactant and Amphiphile Mixtures.

PubMed

Peach, Jocelyn; Czajka, Adam; Hazell, Gavin; Hill, Christopher; Mohamed, Azmi; Pegg, Jonathan C; Rogers, Sarah E; Eastoe, Julian

2017-03-14

For equivalent micellar volume fraction (ϕ), systems containing anisotropic micelles are generally more viscous than those comprising spherical micelles. Many surfactants used in water-in-CO 2 (w/c) microemulsions are fluorinated analogues of sodium bis(2-ethylhexyl) sulfosuccinate (AOT): here it is proposed that mixtures of CO 2 -philic surfactants with hydrotropes and cosurfactants may generate elongated micelles in w/c systems at high-pressures (e.g., 100-400 bar). A range of novel w/c microemulsions, stabilized by new custom-synthesized CO 2 -phillic, partially fluorinated surfactants, were formulated with hydrotropes and cosurfactant. The effects of water content (w = [water]/[surfactant]), surfactant structure, and hydrotrope tail length were all investigated. Dispersed water domains were probed using high pressure small-angle neutron scattering (HP-SANS), which provided evidence for elongated reversed micelles in supercritical CO 2 . These new micelles have significantly lower fluorination levels than previously reported (6-29 wt % cf. 14-52 wt %), and furthermore, they support higher water dispersion levels than other related systems (w = 15 cf. w = 5). The intrinsic viscosities of these w/c microemulsions were estimated based on micelle aspect ratio; from this value a relative viscosity value can be estimated through combination with the micellar volume fraction (ϕ). Combining these new results with those for all other reported systems, it has been possible to "map" predicted viscosity increases in CO 2 arising from elongated reversed micelles, as a function of surfactant fluorination and micellar aspect ratio.

Self-association of analgesics in aqueous solution: micellar properties of dextropropoxyphene hydrochloride and methadone hydrochloride.

PubMed

Attwood, D; Tolley, J A

1980-08-01

The solution properties of several analgesics including dextropropoxyphene hydrochloride, methadone hydrochloride, dextromoramide acid tartrate and dipipanone hydrochloride have been examined using light scattering, conductivity, vapour pressure osmometry and surface tension techniques. A micellar pattern of association was established for dextropropoxyphene hydrochloride and methadone hydrochloride and critical micelle concentrations and aggregation numbers are reported. The hydrophobic contribution to the free energy of micellization of dextropropoxyphene was determined from measurement of the critical micelle concentration in the presence of added electrolyte.

Contrasting Drainage and Stratification in Horizontal Vs Vertical Micellar Foam Films

NASA Astrophysics Data System (ADS)

Wojcik, Ewelina; Yilixiati, Subinuer; Zhang, Yiran; Sharma, Vivek

Understanding and controlling the drainage kinetics of thin films is an important problem that underlies the stability, lifetime and rheology of foams and emulsions. In foam films formed with micellar solutions, the surfactant is present as interfacially-adsorbed layer at both liquid-air interfaces, as well as in bulk as self-assembled supramolecular structures called micelles. Ultrathin micellar films exhibit stratification due to confinement-induced structuring and layering of micelles. Stratification in micellar foam films is manifested as stepwise thinning over time, and it leads to the coexistence of flat domains with discretely different thicknesses. In this contribution we use Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols to visualize and analyze thickness transitions and variations associated with stratification in micellar foam films made with sodium dodecyl sulfate (SDS). We contrast the drainage and stratification dynamics in horizontal and vertical foam films, and investigate the role played by gravitational, viscous, interfacial and surface forces.

Tuning the probe location on zwitterionic micellar system with variation of pH and addition of surfactants with different alkyl chains: solvent and rotational relaxation studies.

PubMed

Banerjee, Chiranjib; Mandal, Sarthak; Ghosh, Surajit; Rao, Vishal Govind; Sarkar, Nilmoni

2012-09-13

In this manuscript, we have modulated the location of an anionic probe, Coumarin-343 (C-343) in a zwitterionic (N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB-16)) micellar system by three different approaches. The effect of addition of the surfactant sodium dodecyl sulfate (SDS) and the room temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium octylsulfate (EmimOs) and N,N-dimethylethanol hexanoate (DAH), to the micellar solution has been studied. The effect of pH variation has been studied as well using solvent and rotational measurements. Migration of the anionic probe, C-343, from the palisade layer of SB-16 micelle to the bulk water has been observed to varying extents with the addition of SDS and EmimOs. The effect is much more pronounced in the presence of SDS and can be ascribed to the presence of the long alkyl (dodecyl) chain on SDS which can easily orient itself and fuse inside the SB-16 micelle and facilitate the observed migration of the probe molecule. This phenomenon is confirmed by faster solvation and rotational relaxation of the investigated probe molecule. The analogous fusion process is difficult in case of EmimOs and DAH because of their comparatively smaller alkyl (octyl and hexanoate) chain. However, the direction of C-343 migration is reversed with the decrease of pH of the SB-16 micellar medium. An increase in the average solvation and rotational relaxation time of the probe in acidic medium has been observed. Since experimental conditions are maintained such that the probe molecules and the zwitterionic SB-16 micelles remain oppositely charged, the observed results can be attributed to the increased electrostatic interaction (attractive) between them. Temperature dependent study also supports this finding.

Separation of flavonol-2-O-glycosides from Calendula officinalis and Sambucus nigra by high-performance liquid and micellar electrokinetic capillary chromatography.

PubMed

Pietta, P; Bruno, A; Mauri, P; Rava, A

1992-02-28

Calendula officinalis and Sambucus nigra flowers were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC) and micellar electrokinetic capillary chromatography (MECC). RP-HPLC was performed on C8 Aquapore RP 300 columns with eluents containing 2-propanol and tetrahydrofuran. MECC was carried out on a 72-cm fused-silica capillary using sodium dodecyl sulphate and sodium borate (pH 8.3) as the running buffer. The results obtained by these techniques are compared.

Principles of Micellar Electrokinetic Capillary Chromatography Applied in Pharmaceutical Analysis

PubMed Central

Hancu, Gabriel; Simon, Brigitta; Rusu, Aura; Mircia, Eleonora; Gyéresi, Árpád

2013-01-01

Since its introduction capillary electrophoresis has shown great potential in areas where electrophoretic techniques have rarely been used before, including here the analysis of pharmaceutical substances. The large majority of pharmaceutical substances are neutral from electrophoretic point of view, consequently separations by the classic capillary zone electrophoresis; where separation is based on the differences between the own electrophoretic mobilities of the analytes; are hard to achieve. Micellar electrokinetic capillary chromatography, a hybrid method that combines chromatographic and electrophoretic separation principles, extends the applicability of capillary electrophoretic methods to neutral analytes. In micellar electrokinetic capillary chromatography, surfactants are added to the buffer solution in concentration above their critical micellar concentrations, consequently micelles are formed; micelles that undergo electrophoretic migration like any other charged particle. The separation is based on the differential partitioning of an analyte between the two-phase system: the mobile aqueous phase and micellar pseudostationary phase. The present paper aims to summarize the basic aspects regarding separation principles and practical applications of micellar electrokinetic capillary chromatography, with particular attention to those relevant in pharmaceutical analysis. PMID:24312804

Formation of highly structured cubic micellar lipid nanoparticles of soy phosphatidylcholine and glycerol dioleate and their degradation by triacylglycerol lipase.

PubMed

Wadsäter, Maria; Barauskas, Justas; Nylander, Tommy; Tiberg, Fredrik

2014-05-28

Lipid nanoparticles of reversed internal phase structures, such as cubic micellar (I2) structure show good drug loading ability of peptides and proteins as well as some small molecules. Due to their controllable small size and inner morphology, such nanoparticles are suitable for drug delivery using several different administration routes, including intravenous, intramuscular, and subcutaneous injection. A very interesting system in this regard, is the two component soy phosphatidylcholine (SPC)/glycerol dioleate (GDO) system, which depending on the ratio of the lipid components form a range of reversed liquid crystalline phases. For a 50/50 (w/w) ratio in excess water, these lipids have been shown to form a reversed cubic micellar (I2) phase of the Fd3m structure. Here, we demonstrate that this SPC/GDO phase, in the presence of small quantities (5-10 wt %) of Polysorbate 80 (P80), can be dispersed into nanoparticles, still with well-defined Fd3m structure. The resulting nanoparticle dispersion has a narrow size distribution and exhibit good long-term stability. In pharmaceutical applications, biodegradation pathways of the drug delivery vehicles and their components are important considerations. In the second part of the study we show how the structure of the particles evolves during exposure to a triacylglycerol lipase (TGL) under physiological-like temperature and pH. TGL catalyzes the lipolytic degradation of acylglycerides, such as GDO, to monoglycerides, glycerol, and free fatty acids. During the degradation, the interior phase of the particles is shown to undergo continuous phase transitions from the reversed I2 structure to structures of less negative curvature (2D hexagonal, bicontinuous cubic, and sponge), ultimately resulting in the formation of multilamellar vesicles.

Spectroscopic and time-dependent density functional investigation of the role of structure on the acid-base effects of citrinin detection

USDA-ARS?s Scientific Manuscript database

A time dependent density functional (TD-DFT) study was carried out on tautomers and ionic forms of citrinin to gain insight into the role of chemical structure and micellar environments on detection. Steady state fluorescence studies of citrinin in micellar aqueous solutions produced unusual results...

Organisation and shape of micellar solutions of block copolymers

NASA Astrophysics Data System (ADS)

Gaspard, J. P.; Creutz, S.; Bouchat, Ph.; Jérôme, R.; Cohen Stuart, M.

1997-02-01

Diblock copolymers of polymethacrylic acid sodium salt, forming the hair, and styrene derivatives have been studied in aqueous solutions by SANS and SAXS. The influence of both the chemical nature and the length of the hydrophobic bloxk on the size and shape of micelles have been investigated. The micellar core size is in agreement with the theoretical evaluation for copolymers with a short hydrophobic sequence. In contrast, in case of larger hydrophobic blocks, the measured size is incompatible with a star-like model. Various hypotheses are presented for the latter.

Microwave enhanced electroanalysis of formulations: processes in micellar media at glassy carbon and at platinum electrodes.

PubMed

Ghanem, Mohamed A; Compton, Richard G; Coles, Barry A; Canals, Antonio; Marken, Frank

2005-10-01

The direct electroanalysis of complex formulations containing alpha-tocopherol (vitamin E) is possible in micellar solution and employing microwave-enhanced voltammetry. In the presence of microwave radiation substantial heating and current enhancement effects have been observed at 330 microm diameter glassy carbon electrodes placed into a micellar aqueous solution and both hydrophilic and highly hydrophobic redox systems are detected. For the water soluble Fe(CN)(6)(3-/4-) redox system in micellar aqueous solutions of 0.1 M NaCl and 0.1 M sodium dodecylsulfate (SDS) at low to intermediate microwave power, thermal effects and convection effects are observed. At higher microwave power, thermal cavitation is induced and dominates the mass transport at the electrode surface. For the micelle-soluble redox systems tert-butylferrocene and 2,5-di-tert-butyl-1,4-benzoquinone, strong and concentration dependent current responses are observed only in the presence of microwave radiation. For the oxidation of micelle-soluble alpha-tocopherol current responses at glassy carbon electrodes are affected by adsorption and desorption processes whereas at platinum electrodes, analytical limiting currents are obtained over a wide range of alpha-tocopherol concentrations. However, for the determination of alpha-tocopherol in a commercial formulation interference from proteins is observed at platinum electrodes and direct measurements are possible only over a limited concentration range and at glassy carbon electrodes.

Microstructural evolution of a model, shear-banding micellar solution during shear startup and cessation.

PubMed

López-Barrón, Carlos R; Gurnon, A Kate; Eberle, Aaron P R; Porcar, Lionel; Wagner, Norman J

2014-04-01

We present direct measurements of the evolution of the segmental-level microstructure of a stable shear-banding polymerlike micelle solution during flow startup and cessation in the plane of flow. These measurements provide a definitive, quantitative microstructural understanding of the stages observed during flow startup: an initial elastic response with limited alignment that yields with a large stress overshoot to a homogeneous flow with associated micellar alignment that persists for approximately three relaxation times. This transient is followed by a shear (kink) band formation with a flow-aligned low-viscosity band that exhibits shear-induced concentration fluctuations and coexists with a nearly isotropic band of homogenous, highly viscoelastic micellar solution. Stable, steady banding flow is achieved only after approximately two reptation times. Flow cessation from this shear-banded state is also found to be nontrivial, exhibiting an initial fast relaxation with only minor structural relaxation, followed by a slower relaxation of the aligned micellar fluid with the equilibrium fluid's characteristic relaxation time. These measurements resolve a controversy in the literature surrounding the mechanism of shear banding in entangled wormlike micelles and, by means of comparison to existing literature, provide further insights into the mechanisms driving shear-banding instabilities in related systems. The methods and instrumentation described should find broad use in exploring complex fluid rheology and testing microstructure-based constitutive equations.

Ionic micelles and aromatic additives: a closer look at the molecular packing parameter.

PubMed

Lutz-Bueno, Viviane; Isabettini, Stéphane; Walker, Franziska; Kuster, Simon; Liebi, Marianne; Fischer, Peter

2017-08-16

Wormlike micellar aggregates formed from the mixture of ionic surfactants with aromatic additives result in solutions with impressive viscoelastic properties. These properties are of high interest for numerous industrial applications and are often used as model systems for soft matter physics. However, robust and simple models for tailoring the viscoelastic response of the solution based on the molecular structure of the employed additive are required to fully exploit the potential of these systems. We address this shortcoming with a modified packing parameter based model, considering the additive-surfactant pair. The role of charge neutralization on anisotropic micellar growth was investigated with derivatives of sodium salicylate. The impact of the additives on the morphology of the micellar aggregates is explained from the molecular level to the macroscopic viscoelasticity. Changes in the micelle's volume, headgroup area and additive structure are explored to redefine the packing parameter. Uncharged additives penetrated deeper into the hydrophobic region of the micelle, whilst charged additives remained trapped in the polar region, as revealed by a combination of 1 H-NMR, SAXS and rheological measurements. A deeper penetration of the additives densified the hydrophobic core of the micelle and induced anisotropic growth by increasing the effective volume of the additive-surfactant pair. This phenomenon largely influenced the viscosity of the solutions. Partially penetrating additives reduced the electrostatic repulsions between surfactant headgroups and neighboring micelles. The resulting increased network density governed the elasticity of the solutions. Considering a packing parameter composed of the additive-surfactant pair proved to be a facile means of engineering the viscoelastic response of surfactant solutions. The self-assembly of the wormlike micellar aggregates could be tailored to desired morphologies resulting in a specific and predictable rheological response.

Sodium triflate decreases interaggregate repulsion and induces phase separation in cationic micelles.

PubMed

Lima, Filipe S; Cuccovia, Iolanda M; Buchner, Richard; Antunes, Filipe E; Lindman, Björn; Miguel, Maria G; Horinek, Dominik; Chaimovich, Hernan

2015-03-10

Dodecyltrimethylammonium triflate (DTATf) micelles possess lower degree of counterion dissociation (α), lower hydration, and higher packing of monomers than other micelles of similar structure. Addition of sodium triflate ([NaTf] > 0.05 M) to DTATf solutions promotes phase separation. This phenomenon is commonly observed in oppositely charged surfactant mixtures, but it is rare for ionic surfactants and relatively simple counterions. While the properties of DTATf have already been reported, the driving forces for the observed phase separation with added salt remain unclear. Thus, we propose an interpretation for the observed phase separation in cationic surfactant solutions. Addition of up to 0.03 M NaTf to micellar DTATf solutions led to a limited increase of the aggregation number, to interface dehydration, and to a progressive decrease in α. The viscosity of DTATf solutions of higher concentration ([DTATf] ≥ 0.06 M) reached a maximum with increasing [NaTf], though the aggregation number slightly increased, and no shape change occurred. We hypothesize that this maximum results from a decrease in interaggregate repulsion, as a consequence of increased ion binding. This reduction in micellar repulsion without simultaneous infinite micellar growth is, probably, the major driving force for phase separation at higher [NaTf].

Morphological transformations in the magnetite biomineralizing protein Mms6 in iron solutions: A small-angle x-ray scattering study

DOE PAGES

Zhang, Honghu; Liu, Xunpei; Feng, Shuren; ...

2015-02-10

In this study, magnetotactic bacteria that produce magnetic nanocrystals of uniform size and well-defined morphologies have inspired the use of biomineralization protein Mms6 to promote formation of uniform magnetic nanocrystals in vitro. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular three-dimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence ofmore » hydroxyl/carboxyl containing residues in the C-terminal domain shuffled) exhibits subtle morphological changes in the presence of iron ions in solutions. The analysis of the SAXS data is consistent with a hierarchical core–corona micellar structure similar to that found in amphiphilic polymers. The addition of ferric and ferrous iron ions to the protein solution induces morphological changes in the micellar structure by transforming the 3D micelles into objects of reduced dimensionality of 2, with fractal-like characteristics (including Gaussian-chain-like) or, alternatively, platelet-like structures.« less

Thermo-reversible morphology and conductivity of a conjugated polymer network embedded in polymeric self-assembly

NASA Astrophysics Data System (ADS)

Han, Youngkyu; Carrillo, Jan-Michael Y.; Zhang, Zhe; Li, Yunchao; Hong, Kunlun; Sumpter, Bobby G.; Ohl, Michael; Paranthaman, Mariappan Parans; Smith, Gregory S.; Do, Changwoo

Self-assembly of block copolymers provides opportunities to create nano hybrid materials, utilizing self-assembled micro-domains with a variety of morphology and periodic architectures as templates for functional nano-fillers. Here we report new progress towards the fabrication of a thermally responsive conducting polymer self-assembly made from a water-soluble poly(thiophene) derivative with short PEO side chains and Pluronic L62 solution in water. The structural and electrical properties of conjugated polymer-embedded nanostructures were investigated by combining SANS, SAXS, CGMD simulations, and impedance spectroscopy. The L62 solution template organizes the conjugated polymers by stably incorporating them into the hydrophilic domains thus inhibiting aggregation. The changing morphology of L62 during the micellar-to-lamellar phase transition defines the embedded conjugated polymer network. The conductivity is strongly coupled to the structural change of the templating L62 phase and exhibits thermally reversible behavior with no signs of quenching of the conductivity at high temperature. The research was sponsored by the Scientific User Facilities Division, Office of BES, U.S. DOE and Laboratory Directed Research and Development Program of ORNL, managed by UT-Battelle, LLC.

Photoreaction of thioxanthone with indolic and phenolic derivatives of biological relevance: magnetic field effect study.

PubMed

Das, Doyel; Nath, Deb Narayan

2008-11-20

The photoinduced reaction of thioxanthone (TX) with various indolic and phenolic derivatives and amino acids like tryptophan and tyrosine has been monitored in sodium dodecyl sulfate micellar medium. Laser flash photolysis and magnetic field effect (MFE) experiments have been used to study the dynamics of the radical pairs. The quenching rate constant with different quenchers in SDS micellar solution has been measured. For indoles the electron-transfer reaction has been found to be followed by proton transfer from the donor molecule, which gives rise to the TX ketyl radical. On the other hand, the electron-transfer reaction in the case of phenols is preceded with formation of a hydrogen-bonded exciplex. The extent of the MFE and magnitude of the magnetic field corresponding to one-half of the saturation value of MFE ( B 1/2) support the fact that hyperfine mechanism plays the primary role. Quenching of MFE in the presence of gadolinium ions confirms that the radical pair is located near the micellar interface. MFE study has been further extended to protein-like bovine serum albumin in micellar solution. The results indicate loss in mobililty of radical pairs in the protein surfactant complex.

Stepwise dynamics of an anionic micellar film - Formation of crown lenses.

PubMed

Lee, Jongju; Nikolov, Alex; Wasan, Darsh

2017-06-15

We studied the stepwise thinning of a microscopic circular foam film formed from an anionic micellar solution of sodium dodecyl sulfate (SDS). The foam film formed from the SDS micellar solution thins in a stepwise manner by the formation and expansion of a dark spot(s) of one layer less than the film thickness. During the last stages of film thinning (e.g., a film with one micellar layer), the dark spot expansion occurs via two steps. Initially, a small dark circular spot inside a film of several microns in size is formed, which expands at a constant rate. Then, a ridge along the expanding spot is formed. As the ridge grows, it becomes unstable and breaks into regular crown lenses, which are seen as white spots in the reflected light at the border of the dark spot with the surrounding thicker film. The Rayleigh type of instability contributes to the formation of the lenses, which results in the increase of the dark spot expansion rate with time. We applied the two-dimensional micellar-vacancy diffusion model and took into consideration the effects of the micellar layering and film volume on the rate of the dark spot expansion [Lee et al., 2016] to predict the rate of the dark spot expansion for a 0.06M SDS film in the presence of lenses. We briefly discuss the Rayleigh type of instability in the case of a 0.06M SDS foam film. The goals of this study are to reveal why the crown lenses are formed during the foam film stratification and to elucidate their effect on the rate of spot expansion. Copyright © 2017 Elsevier Inc. All rights reserved.

Micellar liquid chromatography

NASA Astrophysics Data System (ADS)

Basova, Elena M.; Ivanov, Vadim M.; Shpigun, Oleg A.

1999-12-01

Background and possibilities of practical applications of micellar liquid chromatography (MLC) are considered. Various retention models in MLC, the effects of the nature and concentration of surfactants and organic modifiers, pH, temperature and ionic strength on the MLC efficiency and selectivity are discussed. The advantages and limitations of MLC are demonstrated. The performance of MLC is critically evaluated in relationship to the reversed-phase HPLC and ion-pair chromatography. The potential of application of MLC for the analysis of pharmaceuticals including that in biological fluids and separation of inorganic anions, transition metal cations, metal chelates and heteropoly compounds is described. The bibliography includes 146 references.

Probing pH difference between micellar solution and nanoscale water within common black film by fluorescent dye

NASA Astrophysics Data System (ADS)

Fu, Jingni; Zhang, Luning

2018-03-01

The protonation/deprotonation equilibrium of a fluorescent pH probe (carboxy-seminaphthorhodafluor-1, SNARF-1) within the nanoscale water layer confined in common black films (CBFs) has been studied. We find that SNARF-1 molecules feel a more acidic environment in CBFs than when they are in the bulk micellar solution, using the base/acid peak area ratio of the dye to indicate its microenvironment pH. Three surfactants are used to study the dependence of the pH drop versus charge: cationic (cetyltrimethylammonium bromide, CTAB), anionic (sodium dodecylsulphate, SDS) and nonionic (Triton X-100) species. The decrease of CBFs pH versus the pH of the micellar solution is the following: ΔpH ≈ 1.5 for CTAB (pH: 7.0-9.0), ΔpH ≈ 0.8 for SDS, and ΔpH ≈ 0.4 for Triton X-100. With the addition of electrolyte in CBFs, we observe large decrease the amplitude of the pH anomaly, thus suggesting an electrostatic origin of the pH change at nanoscale environment.

A new insight on the dynamics of sodium dodecyl sulfate aqueous micellar solutions by dielectric spectroscopy.

PubMed

Lanzi, Leandro; Carlà, Marcello; Lanzi, Leonardo; Gambi, Cecilia M C

2009-02-01

Aqueous sodium dodecyl sulfate micellar solutions were investigated by a recently developed double-differential dielectric spectroscopy technique in the frequency range 100 MHz-3 GHz at 22 degrees C, in the surfactant concentration range 29.8-524 mM, explored for the first time above 104 mM. The micellar contribution to dielectric spectra was analyzed according to three models containing, respectively, a single Debye relaxation, a Cole-Cole relaxation and a double Debye relaxation. The single Debye model is not accurate enough. Both Cole-Cole and double Debye models fit well the experimental dielectric spectra. With the double Debye model, two characteristic relaxation times were identified: the slower one, in the range 400-900 ps, is due to the motion of counterions bound to the micellar surface (lateral motion); the faster one, in the range 100-130 ps, is due to interfacial bound water. Time constants and amplitudes of both processes are in fair agreement with Grosse's theoretical model, except at the largest concentration values, where interactions between micelles increase. For each sample, the volume fraction of bulk water and the effect of bound water as well as the conductivity in the low frequency limit were computed. The bound water increases as the surfactant concentration increases, in quantitative agreement with the micellar properties. The number of water molecules per surfactant molecule was also computed. The conductivity values are in agreement with Kallay's model over the whole surfactant concentration range.

Pressure effects on enzyme reactions in mainly organic media: alpha-chymotrypsin in reversed micelles of Aerosol OT in octane.

PubMed

Mozhaev, V V; Bec, N; Balny, C

1994-08-01

Biocatalytic transformations in reversed micelles formed by anionic surfactant Aerosol OT in octane have been studied at high pressures by an example of alpha-chymotrypsin-catalyzed hydrolysis of N-carbobenzoxy-L-tyrosine p-nitrophenyl ester and N-succinyl-L-phenylalanine p-nitroanilide. For the first time it has been found that the enzyme retains high activity in these water-in-oil microemulsions up to a pressure of 2 kbar. The value of the activation volume (delta V*) for the enzyme reactions shows a dependence on the water content in the system. When the size of the micellar aqueous inner cavity (as evaluated at 1 atm) approaches the molecular size of alpha-chymotrypsin, delta V* becomes significantly different from the value in aqueous solution and in the micelles with a larger size. Possibilities of regulating the enzyme activity by pressure in systems with a low content of water are discussed.

Dynamics of adsorption in micellar and non micellar solutions of derivatives of lysosomotropic substances.

PubMed

Dopierala, Katarzyna; Prochaska, Krystyna

2010-04-22

Dynamics of adsorption in micellar and non micellar solutions of derivatives of lysosomotropic substances was studied. The following compounds were considered in our research work: alkyl N,N-dimethyl-alaninates methobromides (DMALM-n), alkyl N,N-dimethylglycinates methobromides (DMGM-n), fatty acids N,N-dimethylaminoethylesters methobromides (DMM-n), fatty acids N,N-dimethylaminopropylesters methobromides (DMPM-n), fatty acids 1-dimethylamino-2-propyl methobromides (DMP(2)M-n), and derivatives of aminoesters with double alkyl chains (M(2)M-n). The examined compounds show interesting biological properties which can be useful, especially in medicine. The exact mechanism of interaction of such compounds with biological membrane is not fully known. However, it is supposed that the presence of micelles has an important role in biological systems. In this paper we show the results of dynamic surface tension measurements in solutions containing the investigated compounds at concentrations above and below cmc. Moreover, we analyzed the influence of the chemical structure of molecules on the diameters of the micelles formed in the solutions. It was found that adsorption dynamics for the studied compounds is strongly affected by the chemical structure of the considered derivatives, especially by the presence of the ester bond, linearity of the molecule, as well as its hydrophobicity. The obtained results show that the structure of the bromide M(2)M-n with two short hydrocarbon chains favors a faster and more efficient adsorption of the molecules at the air/water interface, compared with compounds having one long alkyl chain. Moreover, the double chained derivatives of the M(2)M-n type do not form typical spherical micelles but bilayer structures probably exist in these solutions. The micelles present in the solutions influence the dynamics of adsorption drastically. Moreover, the obtained results indicated that the compounds with especially high biological activity form rather small aggregates. Copyright 2010 Elsevier B.V. All rights reserved.

Suitable combination of promoter and micellar catalyst for kilo fold rate acceleration on benzaldehyde to benzoic acid conversion in aqueous media at room temperature: a kinetic approach.

PubMed

Ghosh, Aniruddha; Saha, Rumpa; Ghosh, Sumanta K; Mukherjee, Kakali; Saha, Bidyut

2013-05-15

The kinetics of oxidation of benzaldehyde by chromic acid in aqueous and aqueous surfactant (sodium dodecyl sulfate, SDS, alkyl phenyl polyethylene glycol, Triton X-100 and N-cetylpyridinium chloride, CPC) media have been investigated in the presence of promoter at 303 K. The pseudo-first-order rate constants (kobs) were determined from a logarithmic plot of absorbance as a function time. The rate constants were found to increase with introduction of heteroaromatic nitrogen base promoters such as Picolinic acid (PA), 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). The product benzoic acid has been characterized by conventional melting point experiment, NMR, HRMS and FTIR spectral analysis. The mechanism of both unpromoted and promoted reaction path has been proposed for the reaction. In presence of the anionic surfactant SDS, cationic surfactant CPC and neutral surfactant TX-100 the reaction can undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Both SDS and TX-100 produce normal micellar effect whereas CPC produce reverse micellar effect in the presence of benzaldehyde. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and bipy combination is the suitable one for benzaldehyde oxidation. Copyright © 2013 Elsevier B.V. All rights reserved.

Fluorescence probe studies of the interactions between poly(oxyethylene) and surfactant micelles and microemulsion droplets in aqueous solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zana, R.; Lianos, P.; Lang, J.

1985-01-03

The interaction between poly(ethylene oxide) (POE) and the aggregates present in micellar solutions of sodium dodecyl sulfate (SDS), mixed micellar solutions of SDS + 1-pentanol, and oil in water microemulsions made of SDS + 1-pentanol + oil (dodecane or toluene) has been investigated by means of fluorescence probing methods. It is shown that the addition of POE results in a decrease of the aggregation number of SDS in the aggregates present in all the systems investigated. Most likely this decrease is due to the adsorption of the POE chain in the micelle palisade layer and the ensuing increase of micellemore » ionization. 22 references, 5 figures, 2 tables.« less

Silica micro- and nanoparticles reduce the toxicity of surfactant solutions.

PubMed

Ríos, Francisco; Fernández-Arteaga, Alejandro; Fernández-Serrano, Mercedes; Jurado, Encarnación; Lechuga, Manuela

2018-04-20

In this work, the toxicity of hydrophilic fumed silica micro- and nanoparticles of various sizes (7 nm, 12 nm, and 50 μm) was evaluated using the luminescent bacteria Vibrio fischeri. In addition, the toxicity of an anionic surfactant solution (ether carboxylic acid), a nonionic surfactant solution (alkyl polyglucoside), and a binary (1:1) mixture of these solutions all containing these silica particles was evaluated. Furthermore, this work discusses the adsorption of surfactants onto particle surfaces and evaluates the effects of silica particles on the surface tension and critical micellar concentration (CMC) of these anionic and nonionic surfactants. It was determined that silica particles can be considered as non-toxic and that silica particles reduce the toxicity of surfactant solutions. Nevertheless, the toxicity reduction depends on the ionic character of the surfactants. Differences can be explained by the different adsorption behavior of surfactants onto the particle surface, which is weaker for nonionic surfactants than for anionic surfactants. Regarding the effects on surface tension, it was found that silica particles increased the surface activity of anionic surfactants and considerably reduced their CMC, whereas in the case of nonionic surfactants, the effects were reversed. Copyright © 2018 Elsevier B.V. All rights reserved.

Self-aggregation of bio-surfactants within ionic liquid 1-ethyl-3-methylimidazolium bromide: A comparative study and potential application in antidepressants drug aggregation

NASA Astrophysics Data System (ADS)

Banjare, Manoj Kumar; Behera, Kamalakanta; Kurrey, Ramsingh; Banjare, Ramesh Kumar; Satnami, Manmohan L.; Pandey, Siddharth; Ghosh, Kallol K.

2018-06-01

Aggregation behavior of bio-surfactants (BS) sodium cholate (NaC) and sodium deoxycholate (NaDC) within aqueous solution of ionic liquid (IL) 1-ethyl-3-methylimidazolium bromide [Emim][Br] has been investigated using surface tension, conductivity, steady state fluorescence, FT-IR and dynamic light scattering (DLS) techniques. Various interfacial and thermodynamic parameters are determined in the presence of different wt% of IL [Emim][Br]. Information regarding the local microenvironment and size of the aggregates is obtained from fluorescence and DLS, respectively. FT-IR spectral response is used to reveal the interactions taking place within aqueous NaC/NaDC micellar solutions. It is noteworthy to mention that increasing wt% of [Emim][Br] results in an increase in the spontaneity of micelle formation and the hydrophilic IL shows more affinity for NaC as compared to NaDC. Further, the micellar solutions of BS-[Emim][Br] are utilized for studying the aggregation of antidepressants drug promazine hydrochloride (pH). UV-vis spectroscopic investigation reveals interesting outcomes and the results show changes in spectral absorbance of PH drug on the addition of micellar solution (BS-[Emim][Br]). Highest binding affinity and most promising activity are shown for NaC as compared to NaDC.

High-frequency ultrasound-responsive block copolymer micelle.

PubMed

Wang, Jie; Pelletier, Maxime; Zhang, Hongji; Xia, Hesheng; Zhao, Yue

2009-11-17

Micelles of a diblock copolymer composed of poly(ethylene oxide) and poly(2-tetrahydropyranyl methacrylate) (PEO-b-PTHPMA) in aqueous solution could be disrupted by high-frequency ultrasound (1.1 MHz). It was found that, upon exposure to a high-intensity focused ultrasound (HIFU) beam at room temperature, the pH value of the micellar solution decreased over irradiation time. The infrared spectroscopic analysis of solid block copolymer samples collected from the ultrasound irradiated micellar solution revealed the formation of carboxylic acid dimers and hydroxyl groups. These characterization results suggest that the high-frequency HIFU beam could induce the hydrolysis reaction of THPMA at room temperature resulting in the cleavage of THP groups. The disruption of PEO-b-PTHPMA micelles by ultrasound was investigated by using dynamic light scattering, atomic force microscopy, and fluorescence spectroscopy. On the basis of the pH change, it was found that the disruption process was determined by a number of factors such as the ultrasound power, the micellar solution volume and the location of the focal spot of the ultrasound beam. This study shows the potential to develop ultrasound-sensitive block copolymer micelles by having labile chemical bonds in the polymer structure, and to use the high-frequency HIFU to trigger a chemical reaction for the disruption of micelles.

HENRY'S LAW CONSTANTS AND MICELLAR PARTITIONING OF VOLATILE ORGANIC COMPOUNDS IN SURFACTANT SOLUTIONS

EPA Science Inventory

Partitioning of volatile organic compounds (VOCs) into surfactant micelles affects the apparent vapor-liquid equilibrium of VOCs in surfactant solutions. This partitioning will complicate removal of VOCs from surfactant solutions by standard separation processes. Headspace expe...

In vitro and in vivo characterisation of PEG-lipid-based micellar complexes of salmon calcitonin for pulmonary delivery.

PubMed

Baginski, Leonie; Gobbo, Oliviero L; Tewes, Frederic; Salomon, Johanna J; Healy, Anne Marie; Bakowsky, Udo; Ehrhardt, Carsten

2012-06-01

To investigate DSPE-PEG(2000)-based micellar formulations of salmon calcitonin (sCT) for their ability to improve pulmonary delivery. Micelles were characterised by DLS and (31)P-NMR spectroscopy. Stability against sCT degrading peptidases, trypsin, α-chymotrypsin and neutrophil elastase as well as their influence on transepithelial absorption was investigated in vitro. In vivo performance of sCT micelles was studied in an experimental model of intratracheal aerosolisation into rats. Micelles with a mean hydrodynamic diameter of 12 nm spontaneously assembled, when a total concentration of 0.02 mM of PEG-lipid and sCT (at 1:1 molar ratio) was exceeded. Nuclear magnetic resonance confirmed the presence of small micellar structures. The micellar formulation showed increased stability against enzymatic digestion. In vitro studies also showed that sCT micelles were able to enhance transepithelial absorption. Data obtained from in vivo experiments provided evidence of significantly (P < 0.05) higher mean plasma concentrations of sCT, after inhalation of micelles compared to sCT solution, at 60 and 90 min, a significantly higher AUC (inf) and a relative bioavailability of 160 ± 55% when compared to plain sCT solution. The herein described PEG-lipid micelles are promising carriers for enhanced pulmonary delivery of sCT.

A Simple and Selective Spectrophotometric Method for the Determination of Trace Gold in Real, Environmental, Biological, Geological and Soil Samples Using Bis (Salicylaldehyde) Orthophenylenediamine

PubMed Central

Soomro, Rubina; Ahmed, M. Jamaluddin; Memon, Najma; Khan, Humaira

2008-01-01

A simple high sensitive, selective, and rapid spectrophotometric method for the determination of trace gold based on the rapid reaction of gold(III) with bis(salicylaldehyde)orthophenylenediamine (BSOPD) in aqueous and micellar media has been developed. BSOPD reacts with gold(III) in slightly acidic solution to form a 1:1 brownish-yellow complex, which has an maximum absorption peak at 490 nm in both aqueous and micellar media. The most remarkable point of this method is that the molar absorptivities of the gold-BSOPD complex form in the presence of the nonionic TritonX-100 surfactant are almost a 10 times higher than the value observed in the aqueous solution, resulting in an increase in the sensitivity and selectivity of the method. The apparent molar absorptivities were found to be 2.3 × 104 L mol−1 cm−1 and 2.5 × 105 L mol−1 cm−1 in aqueous and micellar media, respectively. The reaction is instantaneous and the maximum absorbance was obtained after 10 min at 490 nm and remains constant for over 24 h at room temperature. The linear calibration graphs were obtained for 0.1–30 mg L−1 and 0.01–30 mg L−1 of gold(III) in aqueous and surfactant media, respectively. The interference from over 50 cations, anions and complexing agents has been studied at 1 mg L−1 of Au(III); most metal ions can be tolerated in considerable amounts in aqueous micellar solutions. The Sandell’s sensitivity, the limit of detection and relative standard deviation (n = 9) were found to be 5 ng cm−2, 1 ng mL−1 and 2%, respectively in aqueous micellar solutions. Its sensitivity and selectivity are remarkably higher than that of other reagents in the literature. The proposed method was successfully used in the determination of gold in several standard reference materials (alloys and steels), environmental water samples (potable and polluted), and biological samples (blood and urine), geological, soil and complex synthetic mixtures. The results obtained agree well with those samples analyzed by atomic absorption spectrophotometry (AAS). PMID:19609392

Worming Their Way into Shape: Toroidal Formations in Micellar Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardiel Rivera, Joshua J.; Tonggu, Lige; Dohnalkova, Alice

2013-11-01

We report the formation of nanostructured toroidal micellar bundles (nTMB) from a semidilute wormlike micellar solution, evidenced by both cryogenicelectron microscopy and transmission electron microscopy images. Our strategy for creating nTMB involves a two-step protocol consisting of a simple prestraining process followed by flow through a microfluidic device containing an array of microposts, producing strain rates in the wormlike micelles on the order of 105 s^1. In combination with microfluidic confinement, these unusually large strain rates allow for the formation of stable nTMB. Electron microscopy images reveal a variety of nTMB morphologies and provide the size distribution of the nTMB.more » Small-angle neutron scattering indicates the underlying microstructural transition from wormlike micelles to nTMB. We also show that other flow-induced approaches such as sonication can induce and control the emergence of onion-like and nTMB structures, which may provide a useful tool for nanotemplating.« less

Micellar induced regioselectivity in the two-step consecutive reaction of SO3(2-) with Br-(CH2CH2)n-Br (n=2-5).

PubMed

Currie, Fredrik; Jarvoll, Patrik; Holmberg, Krister; Romsted, Laurence S; Gunaseelan, Krishnan

2007-08-15

High field (800 MHz) (1)H NMR was used to monitor the two-step consecutive reaction of excess SO(3)(2-) with symmetrical bifunctional alpha,omega-dibromoalkanes with butane (DBB), hexane (DBH), octane (DBO), and decane (DBD) chains in CTAB micelles at 25 degrees C. The first-order rate constant for the first substitution step for DBB and DBH is about 5 times faster than for the second, but the kinetics for DBO and DBD were not cleanly first-order. After 40 min, the solution contained about 80% of the intermediate bromoalkanesulfonate from DBB and DBH and the remainder is alkanedisulfonate and unreacted starting material. The same reactions were carried out in homogeneous MeOH/D(2)O solutions at 50 degrees C. The rate constants for all four alpha,omega-dibromoalkanes were first-order throughout the time course of the reaction and the same within +/-10%. However, because micellar solutions are organized on the nanoscale and bring together lipophilic and hydrophilic reactants into a small reaction volume at the micellar interface, they speed this substitution reaction considerably compared to reaction in MeOH/D(2)O. The CTAB micelles also induce a significant regioselectivity in product formation by speeding the first step of the consecutive reaction more than the second. The results are consistent with the bromoalkanesulfonate intermediates having a radial orientation within the micelles with the -CH(2)SO(3)(-) group in the interfacial region and the -CH(2)Br group directed into the micellar core such that the concentration of -CH(2)Br groups in the reactive zone, i.e., the micellar interface, is significantly reduced. These results provide the first example of self-assembled surfactant system altering the relative rates of the reaction steps of a consecutive reaction and, in doing so, enhancing monosubstitution of a symmetrically disubstituted species.

Molecular dynamics shows that ion pairing and counterion anchoring control the properties of triflate micelles: a comparison with triflate at the air/water interface.

PubMed

Lima, Filipe S; Chaimovich, Hernan; Cuccovia, Iolanda M; Horinek, Dominik

2014-02-11

Micellar properties of dodecyltrimethylammonium triflate (DTA-triflate, DTATf) are very different from those of DTA-bromide (DTAB). DTATf aggregates show high aggregation numbers (Nagg), low degree of counterion dissociation (α), disk-like shape, high packing, ordering, and low hydration. These micellar properties and the low surface tension of NaTf aqueous solutions point to a high affinity of Tf(-) to the micellar and air/water interfaces. Although the micellar properties of DTATf are well defined, the source of the Tf(-) effect upon the DTA aggregates is unclear. Molecular dynamics (MD) simulations of Tf(-) (and Br(-)) at the air/water interface and as counterion of a DTA aggregate were performed to clarify the nature of Tf(-) preferences for these interfaces. The effect of NaTf or NaBr on surface tension calculated from MD simulations agreed with the reported experimental values. From the MD simulations a high affinity of Tf(-) toward the interface, which occurred in a specific orientation, was calculated. The micellar properties calculated from the MD simulations for DTATf and DTAB were consistent with experimental data: in MD simulations, the DTATf aggregate was more ordered, packed, and dehydrated than the DTAB aggregate. The Tf(-)/alkyltrimethylammonium interaction energies, calculated from the MD simulations, suggested ion pair formation at the micellar interface, stabilized by the preferential orientation of the adsorbed Tf(-) at the micellar interface.

Interfacial instability of wormlike micellar solutions sheared in a Taylor-Couette cell

NASA Astrophysics Data System (ADS)

Mohammadigoushki, Hadi; Muller, Susan J.

2014-11-01

We report experiments on wormlike micellar solutions sheared in a custom-made Taylor-Couette (TC) cell. The computer controlled TC cell allows us to rotate both cylinders independently. Wormlike micellar solutions containing water, CTAB, and NaNo3 with different compositions are highly elastic and exhibit shear banding. We visualized the flow field in the θ-z as well as r-z planes, using multiple cameras. When subject to low shear rates, the flow is stable and azimuthal, but becomes unstable above a certain threshold shear rate. This shear rate coincides with the onset of shear banding. Visualizing the θ-z plane shows that this instability is characterized by stationary bands equally spaced in the z direction. Increasing the shear rate results to larger wave lengths. Above a critical shear rate, experiments reveal a chaotic behavior reminiscent of elastic turbulence. We also studied the effect of ramp speed on the onset of instability and report an acceleration below which the critical Weissenberg number for onset of instability is unaffected. Moreover, visualizations in the r-z direction reveals that the interface between the two bands undulates with shear bands evolving towards the outer cylinder regardless of which cylinder is rotating.

Molecular simulations of micellar aggregation of polysorbate 20 ester fractions and their interaction with N-phenyl-1-naphthylamine dye.

PubMed

Lapelosa, Mauro; Patapoff, Thomas W; Zarraga, Isidro E

2016-06-01

Micellar aggregation behavior of polysorbate 20 (PS20) has generated significant interest because of the wide use of PS20 as a surfactant to minimize protein surface adsorption and mitigate protein aggregation. Thus, there is a need for better molecular understanding of what drives the biophysical behavior of PS20 in solution. We observe that a complex amphipathic PS20 molecule, which contains both hydrophobic tail and relatively large hydrophilic head, self-associates strongly within the course of a molecular dynamics simulation performed with a fully atomistic representation of the molecule and an explicit water solvent model. The in silico behavior is consistent with micellar models of PS20 in solution. The dynamics of this self-association is rather complex involving both internal reorganization of the molecule and diffusion to form stable micelle-like aggregates. The micellar aggregates of PS20 are long-lived and are formed by the balance between the large hydrophobic interactions associated with the aliphatic tail of PS20, and the steric repulsion of the hydrophilic sorbitan head structure. In the present work, molecular models of PS20 that represent naturally occurring PS20 fractions were produced and characterized in silico. The study investigated the monoester and diester fractions: PS20M, and PS20D. These fractions present differences in the strength of their hydrophobic effect, which influences the aggregation behavior. Adaptive biasing force (ABF) simulations were carried out with the PS20M and PS20D molecular constructs to calculate the free energy of their pairwise interaction. The free energy barrier for the dissociation is higher for PS20D compared with PS20M. The results show that hydrogen bonds can form when head groups are in close proximity, such as in the PS20 aggregate assembly, and the free energy of interaction can be used to predict the morphology of the micellar aggregate for the different PS20 fractions. We were also able to simulate PS20 in the presence of N-phenyl-1-naphthylamine (NPN) to study the solution behavior of the hydrophobic molecule and of the mechanism in which it is sequestered in the hydrophobic core of the PS20 micellar aggregate. Copyright © 2016 Elsevier B.V. All rights reserved.

Self-aggregation of bio-surfactants within ionic liquid 1-ethyl-3-methylimidazolium bromide: A comparative study and potential application in antidepressants drug aggregation.

PubMed

Banjare, Manoj Kumar; Behera, Kamalakanta; Kurrey, Ramsingh; Banjare, Ramesh Kumar; Satnami, Manmohan L; Pandey, Siddharth; Ghosh, Kallol K

2018-06-15

Aggregation behavior of bio-surfactants (BS) sodium cholate (NaC) and sodium deoxycholate (NaDC) within aqueous solution of ionic liquid (IL) 1-ethyl-3-methylimidazolium bromide [Emim][Br] has been investigated using surface tension, conductivity, steady state fluorescence, FT-IR and dynamic light scattering (DLS) techniques. Various interfacial and thermodynamic parameters are determined in the presence of different wt% of IL [Emim][Br]. Information regarding the local microenvironment and size of the aggregates is obtained from fluorescence and DLS, respectively. FT-IR spectral response is used to reveal the interactions taking place within aqueous NaC/NaDC micellar solutions. It is noteworthy to mention that increasing wt% of [Emim][Br] results in an increase in the spontaneity of micelle formation and the hydrophilic IL shows more affinity for NaC as compared to NaDC. Further, the micellar solutions of BS-[Emim][Br] are utilized for studying the aggregation of antidepressants drug promazine hydrochloride (pH). UV-vis spectroscopic investigation reveals interesting outcomes and the results show changes in spectral absorbance of PH drug on the addition of micellar solution (BS-[Emim][Br]). Highest binding affinity and most promising activity are shown for NaC as compared to NaDC. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of salt and surfactant concentration on the structure of polyacrylate gel/surfactant complexes.

PubMed

Nilsson, Peter; Unga, Johan; Hansson, Per

2007-09-20

Small-angle X-ray scattering was used to elucidate the structure of crosslinked polyacrylate gel/dodecyltrimethylammonium bromide complexes equilibrated in solutions of varying concentrations of surfactant and sodium bromide (NaBr). Samples were swollen with no ordering (micelle free), or they were collapsed with either several distinct peaks (cubic Pm3n) or one broad correlation peak (disordered micellar). The main factor determining the structure of the collapsed complexes was found to be the NaBr concentration, with the cubic structure existing up to approximately 150 mM NaBr and above which only the disordered micellar structure was found. Increasing the salt concentration decreases the polyion mediated attractive forces holding the micelles together causing swelling of the gel. At sufficiently high salt concentration the micelle-micelle distance in the gel becomes too large for the cubic structure to be retained, and it melts into a disordered micellar structure. As most samples were above the critical micelle concentration, the bulk of the surfactant was in the form of micelles in the solution and the surfactant concentration thereby had only a minor influence on the structure. However, in the region around 150 mM NaBr, increasing the surfactant concentration, at constant NaBr concentration, was found to change the structure from disordered micellar to ordered cubic and back to disordered again.

Disruption and reassociation of casein micelles under high pressure: influence of milk serum composition and casein micelle concentration.

PubMed

Huppertz, Thom; de Kruif, Cornelis G

2006-08-09

In this study, factors influencing the disruption and aggregation of casein micelles during high-pressure (HP) treatment at 250 MPa for 40 min were studied in situ in serum protein-free casein micelle suspensions. In control milk, light transmission increased with treatment time for approximately 15 min, after which a progressive partial reversal of the HP-induced increase in light transmission occurred, indicating initial HP-induced disruption of casein micelles, followed by reformation of casein aggregates from micellar fragments. The extent of HP-induced micellar disruption was negatively correlated with the concentration of casein micelles, milk pH, and levels of added ethanol, calcium chloride, or sodium chloride and positively correlated with the level of added sodium phosphate. The reformation of casein aggregates during prolonged HP treatment did not occur when HP-induced disruption of casein micelles was limited (<60%) or very extensive (>95%) and was promoted by a low initial milk pH or added sodium phosphate, sodium chloride, or ethanol. On the basis of these findings, a mechanism for HP-induced disruption of casein micelles and subsequent aggregation of micellar fragments is proposed, in which the main element appears to be HP-induced solubilization of micellar calcium phosphate.

A pH-responsive wormlike micellar system of a noncovalent interaction-based surfactant with a tunable molecular structure.

PubMed

Kang, Wanli; Wang, Pengxiang; Fan, Haiming; Yang, Hongbin; Dai, Caili; Yin, Xia; Zhao, Yilu; Guo, Shujun

2017-02-08

Responsive wormlike micelles are very useful in a number of applications, whereas it is still challenging to create dramatic viscosity changes in wormlike micellar systems. Here we developed a pH-responsive wormlike micellar system based on a noncovalent constructed surfactant, which is formed by the complexation of N-erucamidopropyl-N,N-dimethylamine (UC 22 AMPM) and citric acid at the molar ratio of 3 : 1 (EACA). The phase behavior, aggregate microstructure and viscoelasticity of EACA solutions were investigated by macroscopic appearance observation, rheological and cryo-TEM measurements. It was found that the phase behavior of EACA solutions undergoes transition from transparent viscoelastic fluids to opalescent solutions and then phase separation with white floaters upon increasing the pH. Upon increasing the pH from 2.03 to 6.17, the viscosity of wormlike micelles in the transparent solutions continuously increased and reached ∼683 000 mPa s at pH 6.17. As the pH was adjusted to 7.31, the opalescent solution shows a water-like flowing behaviour and the η 0 rapidly declines to ∼1 mPa s. Thus, dramatic viscosity changes of about 6 magnitudes can be triggered by varying the pH values without any deterioration of the EACA system. This drastic variation in rheological behavior is attributed to the pH dependent interaction between UC 22 AMPM and citric acid. Furthermore, the dependence on concentration and temperature of the rheological behavior of EACA solutions was also studied to assist in obtaining the desired pH-responsive viscosity changes.

Micelle-induced versatile sensing behavior of bispyrene-based fluorescent molecular sensor for picric acid and PYX explosives.

PubMed

Ding, Liping; Bai, Yumei; Cao, Yuan; Ren, Guijia; Blanchard, Gary J; Fang, Yu

2014-07-08

The effect of surfactant micelles on the photophysical properties of a cationic bispyrene fluorophore, Py-diIM-Py, was systemically examined. The results from series of measurements including UV-vis absorption, steady-state fluorescence emission, quantum yield, fluorescence lifetime, and time-resolved emission spectra reveal that the cationic fluorophore is only encapsulated by the anionic sodium dodecyl sulfate (SDS) surfactant micelles and not incorporated in the cationic dodecyltrimethylammonium bromide (DTAB) and neutral Triton X-100 (TX100) surfactant micelles. This different fluorophore location in the micellar solutions significantly influences its sensing behavior to various explosives. Fluorescence quenching studies reveal that the simple variation of micellar systems leads to significant changes in the sensitivity and selectivity of the fluorescent sensor to explosives. The sensor exhibits an on-off response to multiple explosives with the highest sensitivity to picric acid (PA) in the anionic SDS micelles. In the cationic DTAB micelles, it displays the highest on-off responses to PYX. Both the sensitivity and selectivity to PYX in the cationic micelles are enhanced compared with that to PA in the anionic micelles. However, the poor encapsulation in the neutral surfactant TX100 micelles leads to fluorescence instability of the fluorophore and fails to function as a sensor system. Time-resolved fluorescence decays in the presence of explosives reveal that the quenching mechanism of two micellar sensor systems to explosives is static in nature. The present work demonstrates that the electrostatic interaction between the cationic fluorophore and differently charged micelles plays a determinative role in adjusting its distribution in micellar solutions, which further influences the sensing behavior of the obtained micellar sensor systems.

Interfacial instability of wormlike micellar solutions sheared in a Taylor-Couette cell

NASA Astrophysics Data System (ADS)

Mohammadigoushki, Hadi; Muller, Susan J.

2014-10-01

We report experiments on wormlike micellar solutions sheared in a custom-made Taylor-Couette (TC) cell. The computer controlled TC cell allows us to rotate both cylinders independently. Wormlike micellar solutions containing water, CTAB, and NaNo3 with different compositions are highly elastic and exhibit shear banding within a range of shear rate. We visualized the flow field in the θ-z as well as r-z planes, using multiple cameras. When subject to low shear rates, the flow is stable and azimuthal, but becomes unstable above a certain threshold shear rate. This shear rate coincides with the onset of shear banding. Visualizing the θ-z plane shows that this instability is characterized by stationary bands equally spaced in the z direction. Increasing the shear rate results to larger wave lengths. Above a critical shear rate, experiments reveal a chaotic behavior reminiscent of elastic turbulence. We also studied the effect of ramp speed on the onset of instability and report an acceleration below which the critical Weissenberg number for onset of instability is unaffected. Moreover, visualizations in the r-z direction reveals that the interface between the two bands undulates. The shear band evolves towards the outer cylinder upon increasing the shear rate, regardless of which cylinder is rotating.

Comparison of micellar extraction combined with ionic liquid based vortex-assisted liquid-liquid microextraction and modified quick, easy, cheap, effective, rugged, and safe method for the determination of difenoconazole in cowpea.

PubMed

Chen, Xiaochu; Bian, Yanli; Liu, Fengmao; Teng, Peipei; Sun, Pan

2017-10-06

Two simple sample pretreatment for the determination of difenoconazole in cowpea was developed including micellar extraction combined with ionic liquid based vortex-assisted liquid-liquid microextraction (ME-IL-VALLME) prior to high performance liquid chromatography (HPLC), and modified quick, easy, cheap, effective, rugged, and safe method (QuEChERS) coupled with HPLC-MS/MS. In ME-IL-VALLME method, the target analyte was extracted by surfactant Tween 20 micellar solution, then the supernatant was diluted with 3mL water to decrease the solubility of micellar solution. Subsequently, the vortex-assisted liquid-liquid microextraction (VALLME) procedure was performed in the diluted extraction solution by using the ionic liquid of 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF 6 ) as the extraction solvent and Tween 20 as an emulsifier to enhance the dispersion of the water-immiscible ionic liquid into the aqueous phase. Parameters that affect the extraction have been investigated in both methods Under the optimum conditions, the limits of quantitation were 0.10 and 0.05mgkg -1 , respectively. And good linearity was achieved with the correlation coefficient higher than 0.9941. The relative recoveries ranged from 78.6 to 94.8% and 92.0 to 118.0% with the relative standard deviations (RSD) of 7.9-9.6% and 1.2-3.2%, respectively. Both methods were quick, simple and inexpensive. However, the ME-IL-VALLME method provides higher enrichment factor compared with conventional QuEChERS method. The ME-IL-VALLME method has a strong potential for the determination of difenoconazole in complex vegetable matrices with HPLC. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of added sodium chloride on the molecular environment and photoionization of N,N,N',N'-tetramethylbenzidine in micellar solutions as studied by electron spin echo and electron spin resonance spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maldonado, R.; Kevan, L.; Szajdzinska-Pietek, E.

1984-11-01

The electron spin echo modulation (ESEM) and electron spin resonance (ESR) spectra of the cation radical of N,N,N',N'-tetramethylbenzidine (TMB) in frozen sodium dodecyl sulfate (SDS)= and dodecyltrimethylammonium chloride (DTAC) micelles were studied as a function of sodium chloride concentration. TMB/sup +center-dot/ was produced by photoionization at 350 nm of the parent compound in the micelles at 77 K. From the ESEM analysis it is found that the cation--water interactions increase with salt addition in both anionic and cationic micelles to a maximum near 0.2 M NaCl and then decrease somewhat. The increase is interpreted in terms of an increase inmore » the water density at the micellar surface due to an increased surface concentration of hydrated counterions. The decrease may be due to TMB moving further from the polar micellar surface with added salt. From ESR spectra the photoionization yields of TMB at 77 K were determined. For DTAC micelles the yields are found to decrease with salt addition as expected from electrostatic considerations. For SDS micelles the photoionization yields increase for salt concentrations up to about 0.15 M and decrease for greater salt concentrations up to 0.5 M. The initial increase in cation yield correlates with electrostatic expectations. The decrease may be due to TMB moving further from the polar micellar surface with added salt. The possible effect of differing TMB protonation equilibria between anionic and cationic micelles on the photoionization yields was found to be unimportant by adjusting the bulk solution pH. An important conclusion is that salt addition can be used to optimize charge separation for photoionized solutes in anionic micelles.« less

Polyelectrolyte-Surfactant Complexes: A New Class of Organogelators

NASA Astrophysics Data System (ADS)

Cavicchi, Kevin; Liu, Yuqing; Guzman, Gustavo

2011-03-01

Polyelectrolyte-surfactant complexes (PE-SURFs) are a class of polymers generated by neutralizing a polyelectrolyte with an oppositely charged surfactant. It has been found that PE-SURFs composed of polystyrene sulfonate and long chain alkyl dimethyl amines act as good organogelators for a range of hydrophobic, organic solvents. Thermo-reversible organogels are formed by heating and cooling PE-SURF/solvent solutions. The gel transition temperature is influenced by the degree of polymerization, the length of the alkyl side-chain, the solubility parameter of the solvent, and the concentration of the gelator. Freeze-drying and scanning electron microscopy characterization of the resultant xerogels shows the formation of rod- and plate-like network morphologies depending on the system parameters. This behavior is consistent with gelation driven by the self-assembly of the amphiphilic PE-SURFs into micellar networks.

Pyrene absorption can be a convenient method for probing critical micellar concentration (cmc) and indexing micellar polarity.

PubMed

Basu Ray, Gargi; Chakraborty, Indranil; Moulik, Satya P

2006-02-01

The critical micellar concentration (cmc) of both ionic and non-ionic surfactants can be conveniently determined from the measurements of UV absorption of pyrene in surfactant solution. The results on a number of surfactants have agreed with that realized from pyrene fluorescence measurements as well as that obtained following conductometric, tensiometric and calorimetric methods. The absorbance vs [surfactant] profiles for all the major UV spectral peaks of pyrene have been found to be sigmoidal in nature which were analyzed according to Sigmoidal-Boltzmann equation (SBE) to evaluate the cmcs of the studied surfactants. The difference between the initial and the final asymptotes (a(i) and a(f), respectively) of the sigmoidal profile, Delta a = (a(f)-a(i)) and the slope of the sigmoid, S(sig) have been observed to depend on the type of the surfactant. The Delta a has shown a linear correlation with the ratio of the fluorescence intensities of the first and the third vibronic peaks, I1/I3 of pyrene which is considered as a measure of the environmental polarity (herein micellar interior) of the probe (pyrene). Thus, Delta a values have the prospect for use as another index for the estimation of polarity of micellar interior.

Characterization and optimization of carboxylesterase-catalyzed esterification between capric acid and glycerol for the production of 1-monocaprin in reversed micellar system.

PubMed

Park, Kyung Min; Kwon, Oh Taek; Ahn, Seon Min; Lee, JaeHwan; Chang, Pahn-Shick

2010-02-28

Calotropis procera R. Br. carboxylesterase (EC 3.1.1.1) solubilized in reversed micellar glycerol droplets containing a very small amount of water (less than 5ppm) and stabilized by a surfactant effectively catalyzed the esterification between glycerol and capric acid to produce 1-monocaprin. Reaction variables including surfactant types, organic solvent media, reaction time, G-value ([glycerol]/[capric acid]), R-value ([water]/[surfactant]), pH, temperature, and types of metal ion inhibitors on the carboxylesterase-catalyzed esterification were characterized and optimized to efficiently produce 1-monocaprin. Bis(2-ethylhexyl) sodium sulfosuccinate (AOT) and isooctane were the most effective surfactant and organic solvent medium, respectively, for 1-monocaprin formation in reversed micelles. The optimum G- and R-values were 3.0 and 0.05, respectively, and the optimum pH and temperature were determined to be 10.0 and 60 degrees C, respectively. K(m,app.) and V(max,app.) were calculated from a Hanes-Woolf plot, and the values were 9.64 mM and 2.45 microM/min mg protein, respectively. Among various metal ions, Cu(2+) and Fe(2+) severely inhibited carboxylesterase-catalyzed esterification activity (less than 6.0% of relative activity). Copyright 2009 Elsevier B.V. All rights reserved.

Quantitative and Mechanistic Assessment of Model Lipophilic Drugs in Micellar Solutions in the Transport Kinetics Across MDR1-MDCK Cell Monolayers.

PubMed

Ho, Norman F H; Nielsen, James; Peterson, Michelle; Burton, Philip S

2016-02-01

An approach to characterizing P-glycoprotein (Pgp) interaction potential for sparingly water-soluble compounds was developed using bidirectional transport kinetics in MDR1-MDCK cell monolayers. Paclitaxel, solubilized in a dilute polysorbate 80 (PS80) micellar solution, was used as a practical example. Although the passage of paclitaxel across the cell monolayer was initially governed by the thermodynamic activity of the micelle-solubilized drug solution, Pgp inhibition was sustained by the thermodynamic activity (i.e., critical micelle concentration) of the PS80 micellar solution bathing the apical (ap) membrane. The mechanistic understanding of the experimental strategies and treatment of data was supported by a biophysical model expressed in the form of transport events occurring at the ap and basolateral (bl) membranes in series whereas the vectorial directions of the transcellular kinetics were accommodated. The derived equations permitted the stepwise quantitative delineation of the Pgp efflux activity (inhibited and uninhibited by PS80) and the passive permeability coefficient of the ap membrane, the passive permeability at the bl membrane and, finally, the distinct coupling of these with efflux pump activity to identify the rate-determining steps and mechanisms. The Jmax/KM(∗) for paclitaxel was in the order of 10(-4) cm/s and the ap- and bl-membrane passive permeability coefficients were asymmetric, with bl-membrane permeability significantly greater than ap. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Unsteady sedimentation of a sphere in wormlike micellar fluids

NASA Astrophysics Data System (ADS)

Zhang, Yiran; Muller, Susan J.

2018-04-01

The unsteady sedimentation of a sphere in wormlike micellar fluids is studied experimentally through shear and extensional rheometry, sphere trajectory tracking, and particle image velocimetry. Unsteady sphere sedimentation characterized by fluctuations in the sphere settling velocity was observed for a range of sphere size and density in two non-shear-banding wormlike micellar solutions, a cetylpyridinium chloride (CpCl)-sodium salicylate (NaSal) solution and a cetyltrimethylammonium p-toluenesulfonate (CTAT)-NaCl solution. The onset of the transition from steady to unsteady sphere motion is characterized by an extensional Deborah number, D eext , defined locally in the negative wake of the falling sphere. This instability criterion is in agreement with previous findings by Mohammadigoushki and Muller [J. Rheol. 60, 587 (2016), 10.1122/1.4948800] in the wormlike micelle system of cetyltrimethylammonium bromide (CTAB) and NaSal, and appears to be universally valid independent of micelle chemistry or solution rheology (e.g., shear banding or not). Moreover, the frequency at which the sphere velocity fluctuates is found to be linearly correlated with an average shear Deborah number D es , which is a measure of the overall flow strength. This suggests that a constant critical strain is accumulated before the flow instability takes place in each velocity oscillation. The velocity fluctuations are found to become increasingly disordered with increasing elastic Mach number, M ae , indicating that the interactions between the flow instability and elastic wave propagation result in more chaotic velocity fluctuations.

One-step synthesis of titania nanoparticles from PS-P4VP diblock copolymer solution

NASA Astrophysics Data System (ADS)

Song, Lixin; Lam, Yeng Ming; Boothroyd, Chris; Teo, Puat Wen

2007-04-01

Polymeric films containing titania nanoparticles have potential as dielectric films for flexible electronic applications. For this purpose, the nanoparticles must be homogeneously distributed. Self-assembly is emerging as a neat, elegant method for fabricating such nanostructured hybrid materials with well-distributed nanoparticles. In this work, we report a micellar solution approach for the assembly of copolymer-titanium precursor nanostructures in which titania nanoparticles were synthesized. The ratio of the amount of titanium precursor, titanium isopropoxide, to the blocks forming the micellar core, poly(4-vinylpyridine), was found to play a key role in controlling film morphology. A sphere-to-ribbon transition was observed when the amount of titanium isopropoxide was increased. The thin film morphology can be tuned using the precursor-copolymer interaction rather than just the polymer-polymer interaction or the polymer-solution interaction. This method provides yet another way to control the morphology of nanostructures.

Prediction of peak shape in hydro-organic and micellar-organic liquid chromatography as a function of mobile phase composition.

PubMed

Baeza-Baeza, J J; Ruiz-Angel, M J; García-Alvarez-Coque, M C

2007-09-07

A simple model is proposed that relates the parameters describing the peak width with the retention time, which can be easily predicted as a function of mobile phase composition. This allows the further prediction of peak shape with global errors below 5%, using a modified Gaussian model with a parabolic variance. The model is useful in the optimisation of chromatographic resolution to assess an eventual overlapping of close peaks. The dependence of peak shape with mobile phase composition was studied for mobile phases containing acetonitrile in the presence and absence of micellised surfactant (micellar-organic and hydro-organic reversed-phase liquid chromatography, RPLC). In micellar RPLC, both modifiers (surfactant and acetonitrile) were observed to decrease or improve the efficiencies in the same percentage, at least in the studied concentration ranges. The study also revealed that the problem of achieving smaller efficiencies in this chromatographic mode, compared to hydro-organic RPLC, is not only related to the presence of surfactant covering the stationary phase, but also to the smaller concentration of organic solvent in the mobile phase.

Stimuli-responsive supramolecular micellar assemblies of cetylpyridinium chloride with cucurbit[5/7]urils.

PubMed

Choudhury, Sharmistha Dutta; Barooah, Nilotpal; Aswal, Vinod Kumar; Pal, Haridas; Bhasikuttan, Achikanath C; Mohanty, Jyotirmayee

2014-05-21

This article demonstrates, for the first time, construction of novel cucurbituril (CB)-adorned supramolecular micellar assemblies of a cationic surfactant, cetylpyridinium chloride (CPC), through noncovalent host-guest interactions. The distinct cation receptor features and cavity dimensions of the CB5 and CB7 homologues assert that the macrocyclic hosts remain complexed with the CPC monomers and take part in the micelle formation, a unique observation in contrast to that of the classical host, β-cyclodextrin. The cooperative contributions of the CB macrocycles in the micelle formation have been documented by the photochemical, surface tension, conductivity, DOSY NMR, and SANS measurements. The contrasting downward and upward shifts in the cmc of the CPC surfactant, respectively, with CB5 and CB7 hosts provide a unique opportunity for the controlled tuning of the micellization region for CPC from 0.57 to 1.6 mM, by using a combination of the macrocyclic hosts. The article also establishes the reversible response of these soft supramolecular micellar structures to thermal-stimuli, which projects their utility for on-demand smart drug-delivery vehicles.

Multiscale Modeling of the Effects of Salt and Perfume Raw Materials on the Rheological Properties of Commercial Threadlike Micellar Solutions.

PubMed

Tang, Xueming; Zou, Weizhong; Koenig, Peter H; McConaughy, Shawn D; Weaver, Mike R; Eike, David M; Schmidt, Michael J; Larson, Ronald G

2017-03-23

We link micellar structures to their rheological properties for two surfactant body-wash formulations at various concentrations of salts and perfume raw materials (PRMs) using molecular simulations and micellar-scale modeling, as well as traditional surfactant packing arguments. The two body washes, namely, BW-1EO and BW-3EO, are composed of sodium lauryl ethylene glycol ether sulfate (SLEnS, where n is the average number of ethylene glycol repeat units), cocamidopropyl betaine (CAPB), ACCORD (which is a mixture of six PRMs), and NaCl salt. BW-3EO is an SLE3S-based body wash, whereas BW-1EO is an SLE1S-based body wash. Additional PRMs are also added into the body washes. The effects of temperature, salt, and added PRMs on micellar lengths, breakage times, end-cap free energies, and other properties are obtained from fits of the rheological data to predictions of the "Pointer Algorithm" [ Zou , W. ; Larson , R.G. J. Rheol. 2014 , 58 , 1 - 41 ], which is a simulation method based on the Cates model of micellar dynamics. Changes in these micellar properties are interpreted using the Israelachvili surfactant packing argument. From coarse-grained molecular simulations, we infer how salt modifies the micellar properties by changing the packing between the surfactant head groups, with the micellar radius remaining nearly constant. PRMs do so by partitioning to different locations within the micelles according to their octanol/water partition coefficient P OW and chemical structures, adjusting the packing of the head and/or tail groups, and by changing the micelle radius, in the case of a large hydrophobic PRM. We find that relatively hydrophilic PRMs with log P OW < 2 partition primarily to the head group region and shrink micellar length, decreasing viscosity substantially, whereas more hydrophobic PRMs, with log P OW between 2 and 4, mix with the hydrophobic surfactant tails within the micellar core and slightly enhance the viscosity and micelle length, which is consistent with the packing argument. Large and very hydrophobic PRMs, with log P OW > 4, are isolated deep inside the micelle, separating from the tails and swelling the radius of the micelle, leading to shorter micelles and much lower viscosities, leading eventually to swollen-droplet micelles.

Interaction between morin and AOT reversed micelles--studies with UV-vis at 25 °C.

PubMed

Bhattarai, Ajaya; Wilczura-Wachnik, H

2014-01-30

The precise measurements of morin absorbance in presence of surfactant/solvent/water systems at 25 °C by UV-vis technique are reported. The surfactant used in presented study was sodium bis(2-ethylhexyl) sulfosuccinate called Aerosol-OT or AOT. The solvents selected were: ethanol, ethylene glycol, and n-decanol. The concentrations of AOT were varied between 0.001 and 0.4 mol/kg. Morin concentration in quvette during UV-vis registration was not equals in all solvent because of its different solubility and absorption intensity depending on the solvent. Water concentration in the studied systems was defined by R parameter according to relation: R=[H2O]/[AOT] and was equal 0, 30 and 40 in ethanol; 0, 10, 20 and 30 in ethylene glycol and 0, 10, 20, 30, and 40 in n-decanol. In presented work a Nernstian distribution of morin between the organic and micellar phases was assumed. The intensity of morin absorbance as a function of AOT concentration was analyzed. Using Non-linear Regression Procedure (NLREG) morin binding constant (K' [mol/kg]), and morin distribution constant (K) between organic phase and AOT micellar phase have been calculated. The experimental results have shown a significant influence of solvent, surfactant and water presence on morin UV-vis spectrum. Calculated data pointed out on different transfer of morin molecules from the organic to micellar phase depending on the solvent. Moreover, results of calculations indicate on competition between morin and water molecules interacting with AOT polar heads. Morin molecules privileged location in AOT reversed micelles strongly depends on the solvent. In case of systems with ethylene glycol as solvent is possible morin molecules location in polar cores of AOT reversed micelles as results of strong interaction between AOT polar heads and morin hydroxyl groups, whereas in case of ethanol and n-decanol morin molecules are located in palisade layer. Copyright © 2013 Elsevier B.V. All rights reserved.

Inhibition mechanism of hydroxypropyl methylcellulose acetate succinate on drug crystallization in gastrointestinal fluid and drug permeability from a supersaturated solution.

PubMed

Ueda, Keisuke; Higashi, Kenjirou; Kataoka, Makoto; Yamashita, Shinji; Yamamoto, Keiji; Moribe, Kunikazu

2014-10-01

The effects of drug-crystallization inhibitor in bile acid/lipid micelles solution on drug permeation was evaluated during the drug crystallization process. Hydroxypropyl methylcellulose acetate succinate (HPMC-AS) was used as a drug-crystallization inhibitor, which efficiently suppressed dexamethasone (DEX) crystallization in a gastrointestinal fluid model containing sodium taurocholate (NaTC) and egg-phosphatidylcholine (egg-PC). Changes of molecular state of supersaturated DEX during the DEX crystallization process was monitored in real time using proton nuclear magnetic resonance (1H NMR). It revealed that DEX distribution to bulk water and micellar phases formed by NaTC and egg-PC was not changed during the DEX crystallization process even in the presence of HPMC-AS. DEX permeation during DEX crystallization was evaluated using dissolution/permeability system. The combination of crystallization inhibition by HPMC-AS and micellar encapsulation by NaTC and egg-PC led to considerably higher DEX concentrations and improvement of DEX permeation at the beginning of the DEX crystallization process. Crystallization inhibition by HPMC-AS can efficiently work even in the micellar solution, where NaTC/egg-PC micelles encapsulates some DEX. It was concluded that a crystallization inhibitor contributed to improvement of permeation of a poorly water-soluble drug in gastrointestinal fluid. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of boiling and frying on the bioaccessibility of beta-carotene in yellow-fleshed cassava roots (Manihot esculenta Crantz cv. BRS Jari).

PubMed

Gomes, Suellen; Torres, Alexandre Guedes; Godoy, Ronoel; Pacheco, Sidney; Carvalho, José; Nutti, Marília

2013-03-01

The effects of boiling and frying on the bioaccessibility of all-trans-beta-carotene in biofortified BRS Jari cassava roots have not been investigated, although these are conventional methods of cassava preparation. The aims of the present study were to investigate beta-carotene micellarization efficiency of yellow-fleshed BRS Jari cassava roots after boiling and frying, as an indicator of the bioaccessibility of this carotenoid, and to apply fluorescence microscopy to investigate beta-carotene in the emulsified fraction. Uncooked, boiled, and fried cassava roots were digested in vitro for the evaluation, by reversed-phase high-performance liquid chromatography (HPLC), of the efficiency of micellarization of all-trans-beta-carotene in BRS Jari cassava roots. Fluorescence microscopy of the micellar fraction was used to confirm the presence of beta-carotene in the emulsified fraction and to observe the structure of the microemulsion from the boiled and fried cassava samples. Fried cassava roots showed the highest (p < .05) micellarization efficiency for total carotenoids and all-trans-beta-carotene (14.1 +/- 2.25% and 14.37 +/- 2.44%, respectively), compared with boiled and raw samples. Fluorescence microscopy showed that after in vitro digestion there were no carotenoid crystals in the micellar fraction, but rather that this fraction presented a biphasic system compatible with emulsified carotenoids, which was consistent with the expected high bioavailability of beta-carotene in this fraction. Increased emulsification and bioaccessibility of beta-carotene from fried biofortified BRS Jari cassava roots compensates for chemical losses during preparation, indicating that this preparation is suitable for home use of BRS Jari cassava roots and might represent a relatively good food source of bioavailable provitamin A.

Simultaneous determination of micellar structure and drag reduction in a surfactant solution flow using the fluorescence probe method

NASA Astrophysics Data System (ADS)

Wakimoto, Tatsuro; Araga, Koichi; Katoh, Kenji

2018-03-01

As widely known, the addition of a specific type of surfactant to water reduces drag in a pipe flow. This effect is considered to be a result of the suppression of turbulent transition caused by the ordered structure of rod-like micelles that is referred to as a shear-induced structure (SIS). However, it is typically difficult to determine the SIS since it is necessary to noninvasively detect the SIS with several hundred nanometers in the actual moving flow. In this study, we used the fluorescence probe method to locally determine the SIS in a pipe flow. When hydrophobic fluorescence molecules are added to the surfactant solution, the fluorescence molecules are trapped in micelles. Thus, fluorescence intensity varies based on the change in the micellar structure. We verified the applicability of the fluorescence probe method to the SIS detection and determined the relationship between the micellar structure and the drag reduction in the pipe flow by simultaneously measuring the fluorescence intensity and pipe friction factor. The experimental result demonstrates that the SIS formation in the near-wall region is closely correlated with the drag reduction and suggests that the near-wall SIS suppresses the turbulent transition.

Predicting drug penetration across the blood-brain barrier: comparison of micellar liquid chromatography and immobilized artificial membrane liquid chromatography.

PubMed

De Vrieze, Mike; Lynen, Frédéric; Chen, Kai; Szucs, Roman; Sandra, Pat

2013-07-01

Several in vitro methods have been tested for their ability to predict drug penetration across the blood-brain barrier (BBB) into the central nervous system (CNS). In this article, the performance of a variety of micellar liquid chromatographic (MLC) methods and immobilized artificial membrane (IAM) liquid chromatographic approaches were compared for a set of 45 solutes. MLC measurements were performed on a C18 column with sodium dodecyl sulfate (SDS), polyoxyethylene (23) lauryl ether (Brij35), or sodium deoxycholate (SDC) as surfactant in the micellar mobile phase. IAM liquid chromatography measurements were performed with Dulbecco's phosphate-buffered saline (DPBS) and methanol as organic modifier in the mobile phase. The corresponding retention and computed descriptor data for each solute were used for construction of models to predict transport across the blood-brain barrier (log BB). All data were correlated with experimental log BB values and the relative performance of the models was studied. SDS-based models proved most suitable for prediction of log BB values, followed closely by a simplified IAM method, in which it could be observed that extrapolation of retention data to 0% modifier in the mobile phase was unnecessary.

Towards neutron scattering experiments with sub-millisecond time resolution

DOE PAGES

Adlmann, F. A.; Gutfreund, Phillip; Ankner, John Francis; ...

2015-02-01

Neutron scattering techniques offer several unique opportunities in materials research. However, most neutron scattering experiments suffer from the limited flux available at current facilities. This limitation becomes even more severe if time-resolved or kinetic experiments are performed. A new method has been developed which overcomes these limitations when a reversible process is studied, without any compromise on resolution or beam intensity. We demonstrate that, by recording in absolute time the neutron detector events linked to an excitation, information can be resolved on sub-millisecond timescales. Specifically, the concept of the method is demonstrated by neutron reflectivity measurements in time-of-flight mode atmore » the Liquids Reflectometer located at the Spallation Neutron Source, Oak Ridge National Laboratory, Tennessee, USA, combined with in situ rheometry. Finally, the opportunities and limitations of this new technique are evaluated by investigations of a micellar polymer solution offering excellent scattering contrast combined with high sensitivity to shear.« less

Amphiphilic Imbalance and Stabilization of Block Copolymer Micelles on-Demand through Combinational Photo-Cleavage and Photo-Crosslinking.

PubMed

Zhang, Xuan; Wang, Youpeng; Li, Guo; Liu, Zhaotie; Liu, Zhongwen; Jiang, Jinqiang

2017-01-01

An amphiphilic block copolymer of poly(ethylene oxide)-b-poly((N-methacryloxy phthalimide)-co-(7-(4-vinyl-benzyloxyl)-4-methylcoumarin)) (PEO 45 -b-P(MAPI 36 -co-VBC 4 )) is designed to improve the micellar stability during the photo-triggered release of hydrophobic cargoes. Analysis of absorption and emission spectra, solution transmittance, dynamic light scattering, and transmission electron microscopy supports that polymer micelles of PEO 45 -b-P(MAPI 36 -co-VBC 4 ) upon the combinational irradiation of 365 and 254 nm light can be solubilized through the photolysis of phthalimide esters and simultaneously crosslinked via the partially reversible photo-dimerization of coumarins. The photo-triggered release experiment shows that the leakage of doxorubicin molecules from crosslinked micelles can be predictably regulated by controlling the irradiation time of 365 and 254 nm light. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Switching wormlike micelles of selenium-containing surfactant using redox reaction.

PubMed

Zhang, Yongmin; Kong, Weiwei; Wang, Cheng; An, Pengyun; Fang, Yun; Feng, Yujun; Qin, Zhirong; Liu, Xuefeng

2015-10-14

A novel redox-switchable wormlike micellar system was developed based on a mixture of selenium-containing zwitterionic surfactant and commercially available anionic surfactant sodium dodecyl sulfate, which reversibly and quickly responds to H2O2 and vitamin C, and shows circulatory gel/sol transition, reflecting changes in aggregate morphology from entangled worms to vesicles.

Encapsulation Efficiency and Micellar Structure of Solute-Carrying Block Copolymer Nanoparticles

PubMed Central

Woodhead, Jeffrey L.; Hall, Carol K.

2011-01-01

We use discontinuous molecular dynamics (DMD) computer simulation to investigate the encapsulation efficiency and micellar structure of solute-carrying block copolymer nanoparticles as a function of packing fraction, polymer volume fraction, solute mole fraction, and the interaction parameters between the hydrophobic head blocks and between the head and the solute. The encapsulation efficiency increases with increasing polymer volume fraction and packing fraction but decreases with increasing head-head interaction strength. The latter is due to an increased tendency for the solute to remain on the micelle surface. We compared two different nanoparticle assembly methods, one in which the solute and copolymer co-associate and the other in which the copolymer micelle is formed before the introduction of solute. The assembly method does not affect the encapsulation efficiency but does affect the solute uptake kinetics. Both head-solute interaction strength and head-head interaction strength affect the density profile of the micelles; increases in the former cause the solute to distribute more evenly throughout the micelle, while increases in the latter cause the solute to concentrate further from the center of the micelle. We explain our results in the context of a model of drug insertion into micelles formulated by Kumar and Prud’homme; as conditions become more conducive to micelle formation, a stronger energy barrier to solute insertion forms which in turn decreases the encapsulation efficiency of the system. PMID:21918582

Reverse micelle synthesis of oxide nanopowders: mechanisms of precipitate formation and agglomeration effects.

PubMed

Graeve, Olivia A; Fathi, Hoorshad; Kelly, James P; Saterlie, Michael S; Sinha, Kaustav; Rojas-George, Gabriel; Kanakala, Raghunath; Brown, David R; Lopez, Enrique A

2013-10-01

We present an analysis of reverse micelle stability in four model systems. The first two systems, composed of unstable microemulsions of isooctane, water, and Na-AOT with additions of either iron sulfate or yttrium nitrate, were used for the synthesis of iron oxide or yttrium oxide powders. These oxide powders were of nanocrystalline character, but with some level of agglomeration that was dependent on calcination temperature and cleaning procedures. Results show that even though the reverse micellar solutions were unstable, nanocrystalline powders with very low levels of agglomeration could be obtained. This effect can be attributed to the protective action of the surfactant on the surfaces of the powders that prevents neck formation until after all the surfactant has volatilized. A striking feature of the IR spectra collected on the iron oxide powders is the absence of peaks in the ~1715 cm(-1) to 1750 cm(-1) region, where absorption due to the symmetric C=O (carbonyl) stretching occurs. The lack of such peaks strongly suggests the carbonyl group is no longer free, but is actively participating in the surfactant-precipitate interaction. The final two microemulsion systems, containing CTAB as the surfactant, showed that loss of control of the reverse micelle synthesis process can easily occur when the amount of salt in the water domains exceeds a critical concentration. Both model systems eventually resulted in agglomerated powders of broad size distributions or particles that were large compared to the sizes of the reverse micelles, consistent with the notion that the microemulsions were not stable and the powders were precipitated in an uncontrolled fashion. This has implications for the synthesis of nanopowders by reverse micelle synthesis and provides a benchmark for process control if powders of the highest quality are desired. Copyright © 2013 Elsevier Inc. All rights reserved.

Structural changes of casein micelles in a calcium gradient film.

PubMed

Gebhardt, Ronald; Burghammer, Manfred; Riekel, Christian; Roth, Stephan Volkher; Müller-Buschbaum, Peter

2008-04-09

Calcium gradients are prepared by sequentially filling a micropipette with casein solutions of varying calcium concentration and spreading them on glass slides. The casein film is formed by a solution casting process, which results in a macroscopically rough surface. Microbeam grazing incidence small-angle X-ray scattering (microGISAXS) is used to investigate the lateral size distribution of three main components in casein films: casein micelles, casein mini-micelles, and micellar calcium phosphate. At length scales within the beam size the film surface is flat and detection of size distribution in a macroscopic casein gradient becomes accessible. The model used to analyze the data is based on a set of three log-normal distributed particle sizes. Increasing calcium concentration causes a decrease in casein micelle diameter while the size of casein mini-micelles increases and micellar calcium phosphate particles remain unchanged.

(Charge separation in photoredox reactions). Informal annual technical progress report, October 1, 1981-October 1, 1982. [N,N,N',N'tetramethylbenzidine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevan, L.

1982-10-21

During this period work has focused on the structural aspects of photoinduced charge separation in micellar media with initial forays into vesicular media. The primary techniques utilized are electron spin resonance and electron spin echo spectrometry. The analysis of electron spin echo modulation gives a unique handle on very weak hyperfine interactions thus providing a new structural tool for this general problem. Electron spin resonance and electron spin echo studies of the photoionization of N,N,N',N'tetramethylbenzidine (TMB) to give the cation radical have been carried out in anionic, cationic and nonionic micellar solutions frozen to 77/sup 0/K. The photoionization efficiency ofmore » TMB has also been studied in micelles with varying alkyl chain lengths of the surfactant. Stearic acid nitroxide spin probes have also been used to determine some structural aspects of the location of the neutral TMB molecule in anionic micelles before photoionization. The nitroxide work in which the nitroxide is acting as an electron acceptor also shows that a suitable electron acceptor can be located within the micellar structure. The effect of inorganic solutes on the efficiency of the photoionization of TMB in frozen micelles has also been studied. A series of electron scavenger studies have been initiated to study the effect on TMB photoionization efficiency. Electron spin echo detection of laser photogenerated TMB cation in liquid sodium dodecyl sulfate solutions at room temperature has recently been observed.« less

Applications of micellar enzymology to clean coal technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walsh, C.T.

1990-10-26

This project is designed to develop methods for pre-combustion coal remediation by implementing recent advances in enzyme biochemistry. The novel approach of this study is incorporation of hydrophilic oxidative enzymes in reverse micelles in an organic solvent. Enzymes from commercial sources or microbial extracts are being investigated for their capacity to remove organic sulfur from coal by oxidation of the sulfur groups, splitting of C-S bonds and loss of sulfur as sulfuric acid Dibenzothiophene (DBT) and ethlyphenylsulfide (EPS) are serving as models of organic sulfur-containing components of coal in initial studies. A goal of this project is to define amore » reverse micelle system that optimizes the catalytic activity of enzymes toward desulfurization of model compounds and ultimately coal samples. Among the variables which will be examined are the surfactant, the solvent, the water:surfactant ration and the pH and ionic strength of the aqueous phase. Studies were carried out with HRP, Type I RZ=1.2 and Type VI RZ=3.2 and laccase from Polyporus versicolor. Substrates for HRP assays included hydrogen peroxide, DBT, DBT sulfoxide, and DBT sulfone. Buffers included sodium phosphate. For formation of reverse micelle solutions the surfactant AOT, di(2-ethyl-hexyl)sodium sulphosuccinate, was obtained from Sigma Chemical Co. Isooctant was used as organic solvent. 12 refs., 5 figs., 3 tabs.« less

Deciphering the fluorescence resonance energy transfer from denatured transport protein to anthracene 1,5 disulphonate in reverse micellar environment

NASA Astrophysics Data System (ADS)

Singharoy, Dipti; Bhattacharya, Subhash Chandra

2017-12-01

Constrained environmental effect inside AOT reverse micellar media has been employed in this work to collect the information about energy transfer efficacy between sodium salt of anthracene 1,5 disulphonate (1,5-AS) with model transport proteins, bovine serum albumin (BSA), and human serum albumin (HSA). Steady state, time-resolved fluorescence and circular dichroism techniques have been used for this purpose and corresponding Fӧrster-type resonance energy transfer (FRET) from tryptophan residues to 1,5-AS indicates that 1,5-AS binds in the vicinity of the tryptophan residue (BSA and HSA) with equal strength. Indication of protein damage from fluorescence data and its confirmation has been measured from CD measurement. Molecular modeling study hereby plays a crucial role to predict the minimum energy docked conformation of the probe inside the protein environment. From the docked conformation the distance between 1,5-AS and tryptophan moiety of BSA/HSA has successfully explained the FRET possibility between them. A comparative modeling study between BSA and HSA with 1,5-AS assigning their binding site within specific amino acids plays a crucial role in support of the FRET study.

Protons in non-ionic aqueous reverse micelles.

PubMed

Rodriguez, Javier; Martí, Jordi; Guàrdia, Elvira; Laria, Daniel

2007-05-03

Using molecular dynamics techniques, we investigate the solvation of an excess proton within an aqueous reverse micelle in vacuo, with the neutral surfactant diethylene glycol monodecyl ether [CH3(CH2)11(OC2H4)2OH]. The simulation experiments were performed using a multistate empirical valence bond Hamiltonian model. Our results show that the stable solvation environments for the excess proton are located in the water-surfactant interface and that its first solvation shell is composed exclusively by water molecules. The relative prevalence of Eigen- versus Zundel-like solvation structures is investigated; compared to bulk results, Zundel-like structures in micelles become somewhat more stable. Characteristic times for the proton translocation jumps have been computed using population relaxation time correlation functions. The micellar rate for proton transfer is approximately 40x smaller than that found in bulk water at ambient conditions. Differences in the computed rates are examined in terms of the hydrogen-bond connectivity involving the first solvation shell of the excess charge with the rest of the micellar environment. Simulation results would indicate that proton transfers are correlated with rare episodes during which the HB connectivity between the first and second solvation shells suffers profound modifications.

Synergistic cosolubilization of omega-3 fatty acid esters and CoQ10 in dilutable microemulsions.

PubMed

Deutch-Kolevzon, Rivka; Aserin, Abraham; Garti, Nissim

2011-10-01

Water-dilutable microemulsions were prepared and loaded with two types of omega-3 fatty acid esters (omega-3 ethyl esters, OEE; and omega-3 triacylglycerides, OTG), each separately and together with ubiquinone (CoQ(10)). The microemulsions showed high and synergistic loading capabilities. The linear fatty acid ester (OEE) solubilization capacity was greater than that of the bulky and robust OTG. The location of the guest molecules within the microemulsions at any dilution point were determined by electrical conductivity, viscosity, DSC, SAXS, cryo-TEM, SD-NMR, and DLS. We found that OEE molecules pack well within the surfactant tails to form reverse micelles that gradually, upon water dilution, invert into bicontinuous phase and finally into O/W droplets. The CoQ(10) increases the stabilization and solubilization of the omega-3 fatty acid esters because it functions as a kosmotropic agent in the micellar system. The hydrophobic and bulky OTG molecule strongly interferes with the tail packing and spaces them significantly - mainly in the low and medium range water dilutions. When added to the micellar system, CoQ(10) forms some reverse hexagonal mesophases. The inversion into direct micelles is more difficult in comparison to the OEE system and requires additional water dilution. The OTG with or without CoQ(10) destabilizes the structures and decreases the solubilization capacity since it acts as a chaotropic agent to the micellar system and as a kosmotropic agent to hexagonal packing. These results explain the differences in the behavior of these molecules with vehicles that solubilize them in aqueous phases. Temperature disorders the bicontinuous structures and reduces the supersaturation of the system containing OEE with CoQ(10); as a result CoQ(10) crystallization is retarded. Copyright © 2011. Published by Elsevier Ireland Ltd.

A novel, rapid and automated conductometric method to evaluate surfactant-cells interactions by means of critical micellar concentration analysis.

PubMed

Tiecco, Matteo; Corte, Laura; Roscini, Luca; Colabella, Claudia; Germani, Raimondo; Cardinali, Gianluigi

2014-07-25

Conductometry is widely used to determine critical micellar concentration and micellar aggregates surface properties of amphiphiles. Current conductivity experiments of surfactant solutions are typically carried out by manual pipetting, yielding some tens reading points within a couple of hours. In order to study the properties of surfactant-cells interactions, each amphiphile must be tested in different conditions against several types of cells. This calls for complex experimental designs making the application of current methods seriously time consuming, especially because long experiments risk to determine alterations of cells, independently of the surfactant action. In this paper we present a novel, accurate and rapid automated procedure to obtain conductometric curves with several hundreds reading points within tens of minutes. The method was validated with surfactant solutions alone and in combination with Saccharomyces cerevisiae cells. An easy-to use R script, calculates conductometric parameters and their statistical significance with a graphic interface to visualize data and results. The validations showed that indeed the procedure works in the same manner with surfactant alone or in combination with cells, yielding around 1000 reading points within 20 min and with high accuracy, as determined by the regression analysis. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Stagnation point flow of wormlike micellar solutions in a microfluidic cross-slot device: effects of surfactant concentration and ionic environment.

PubMed

Haward, Simon J; McKinley, Gareth H

2012-03-01

We employ the techniques of microparticle image velocimetry and full-field birefringence microscopy combined with mechanical measurements of the pressure drop to perform a detailed characterization of the extensional rheology and elastic flow instabilities observed for a range of wormlike micellar solutions flowing through a microfluidic cross-slot device. As the flow rate through the device is increased, the flow first bifurcates from a steady symmetric to a steady asymmetric configuration characterized by a birefringent strand of highly aligned micellar chains oriented along the shear-free centerline of the flow field. At higher flow rates the flow becomes three dimensional and time dependent and is characterized by aperiodic spatiotemporal fluctuations of the birefringent strand. The extensional properties and critical conditions for the onset of flow instabilities in the fluids are highly dependent on the fluid formulation (surfactant concentration and ionic strength) and the resulting changes in the linear viscoelasticity and nonlinear shear rheology of the fluids. By combining the measurements of critical conditions for the flow transitions with the viscometric material properties and the degree of shear-thinning characterizing each test fluid, it is possible to construct a stability diagram for viscoelastic flow of complex fluids in the cross-slot geometry.

Global optimization of cholic acid aggregates

NASA Astrophysics Data System (ADS)

Jójárt, Balázs; Viskolcz, Béla; Poša, Mihalj; Fejer, Szilard N.

2014-04-01

In spite of recent investigations into the potential pharmaceutical importance of bile acids as drug carriers, the structure of bile acid aggregates is largely unknown. Here, we used global optimization techniques to find the lowest energy configurations for clusters composed between 2 and 10 cholate molecules, and evaluated the relative stabilities of the global minima. We found that the energetically most preferred geometries for small aggregates are in fact reverse micellar arrangements, and the classical micellar behaviour (efficient burial of hydrophobic parts) is achieved only in systems containing more than five cholate units. Hydrogen bonding plays a very important part in keeping together the monomers, and among the size range considered, the most stable structure was found to be the decamer, having 17 hydrogen bonds. Molecular dynamics simulations showed that the decamer has the lowest dissociation propensity among the studied aggregation numbers.

Mass transport in micellar surfactant solutions: 2. Theoretical modeling of adsorption at a quiescent interface.

PubMed

Danov, K D; Kralchevsky, P A; Denkov, N D; Ananthapadmanabhan, K P; Lips, A

2006-01-31

Here, we apply the detailed theoretical model of micellar kinetics from part 1 of this study to the case of surfactant adsorption at a quiescent interface, i.e., to the relaxation of surface tension and adsorption after a small initial perturbation. Our goal is to understand why for some surfactant solutions the surface tension relaxes as inverse-square-root of time, 1/t(1/2), but two different expressions for the characteristic relaxation time are applicable to different cases. In addition, our aim is to clarify why for other surfactant solutions the surface tension relaxes exponentially. For this goal, we carried out a computer modeling of the adsorption process, based on the general system of equations derived in part 1. This analysis reveals the existence of four different consecutive relaxation regimes (stages) for a given micellar solution: two exponential regimes and two inverse-square-root regimes, following one after another in alternating order. Experimentally, depending on the specific surfactant and method, one usually registers only one of these regimes. Therefore, to interpret properly the data, one has to identify which of these four kinetic regimes is observed in the given experiment. Our numerical results for the relaxation of the surface tension, micelle concentration and aggregation number are presented in the form of kinetic diagrams, which reveal the stages of the relaxation process. At low micelle concentrations, "rudimentary" kinetic diagrams could be observed, which are characterized by merging of some stages. Thus, the theoretical modeling reveals a general and physically rich picture of the adsorption process. To facilitate the interpretation of experimental data, we have derived convenient theoretical expressions for the time dependence of surface tension and adsorption in each of the four regimes.

Charge separation in photoredox reactions. Technical progress report, May 1, 1981-May 1, 1984. [N,N,N',N'-tetramethylbenzidine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevan, L.

1984-05-01

The structural aspects controlling charge separation in molecular photoionization reactions in organized molecular assemblies involving micelles and vesicles are being studied by optical and electron magnetic resonance techniques including the time domain technique of electron spin echo modulation (ESEM). Photoionization of N,N,N',N'-tetramethylbenzidine (TMB) to give the cation radical has been carried out in both liquid and frozen micellar and vesicular solutions. Cation-water interactions have been detected by ESEM analysis and indicate that the cation is localized asymmetrically within these organized molecular assemblies. x-Doxylstearic acid spin probes have been used to determine that the neutral TMB molecule before photoionization is alsomore » localized asymmetrically within such organized molecular assemblies. Electron spin echo detection of laser photogenerated TMB cation in liquid micellar solutions gives a direct measurement of the phase memory magnetic relaxation time which gives additional structural information. The photoionization efficiency has been related to cation-water interactions measured by ESEM. The photoionization efficiency is also dependent on surface charge and is about twofold greater in cationic micelles and vesicles compared to anionic micelles and vesicles. TMB is in a less polar environment in vesicles compared to micelles consistent with ESEM results. The preferential adsorption of metal species at micellar surfaces has been detected by ESEM. Modifications in the micelle surface have been effected by added salts and varying counterions which have been related to cation-water interactions and to the TMB photoionization efficiency. Corresponding changes in the surface and internal micellar structure have been investigated by x-doxylstearic acid spin probes and specifically deuterated surfactants. The decay kinetics of TMB cations in micelles have been interpreted in terms of a time dependent rate constant.« less

A new application of micellar liquid chromatography in the determination of free ampicillin concentration in the drug-human serum albumin standard solution in comparison with the adsorption method.

PubMed

Stępnik, Katarzyna E; Malinowska, Irena; Maciejewska, Małgorzata

2016-06-01

The determination of free drug concentration is a very important issue in the field of pharmacology because only the unbound drug fraction can achieve a pharmacological effect. Due to the ability to solubilize many different compounds in micellar aggregates, micellar liquid chromatography (MLC) can be used for direct determination of free drug concentration. Proteins are not retained on the stationary phase probably due to the formation of protein - surfactant complexes which are excluded from the pores of stationary phase. The micellar method is simple and fast. It does not require any pre-preparation of the tested samples for analysis. The main aim of this paper is to demonstrate a completely new applicability of the analytical use of MLC concerning the determination of free drug concentration in the standard solution of human serum albumin. The well-known adsorption method using RP-HPLC and the spectrophotometric technique was applied as the reference method. The results show that the free drug concentration value obtained in the MLC system (based on the RP-8 stationary phase and CTAB) is similar to that obtained by the adsorption method: both RP-HPLC (95.83μgmL(-1), 79.86% of free form) and spectrophotometry (95.71μgmL(-1), 79.76%). In the MLC the free drug concentration was 93.98μgmL(-1) (78.3%). This indicates that the obtained results are within the analytical range of % of free ampicillin fraction and the MLC with direct sample injection can be treated like a promising method for the determination of free drug concentration. Copyright © 2016 Elsevier B.V. All rights reserved.

Micellar catalyzed degradation of fenitrothion, an organophosphorus pesticide, in solution and soils.

PubMed

Balakrishnan, Vimal K; Buncel, Erwin; Vanloon, Gary W

2005-08-01

We report on a study of the decomposition of fenitrothion (an organophosphorus pesticide that is a persistent contaminant in soils and groundwater) as catalyzed by cetyltrimethylammonium (CTA+) micelles. The CTA micelles were associated with two types of counterions: (1) inert counterions (e.g. CTABr) and (2) reactive counterions (e.g. CTAOH). The reactive counterion surfactants used were hydroxide anion (HO-) as a normal nucleophile and hydroperoxide anion (HOO-) and the anion of pyruvaldehyde oxime (MINA-) as two alpha-nucleophiles. The reactivity order followed: CTABr < CTAOH < CTAMINA < CTAOOH. Treatment of the rate data using the Pseudo-Phase Ion Exchange (PPIE) model of micellar catalysis showed the ratio k2M/k2w to be less than unity for all the surfactants employed. Rather than arising from a "true catalysis", we attributed the observed rate enhancements to a "concentration effect", where both pesticide and nucleophile were incorporated into the small micellar phase volume. Furthermore, the CTAOOH/CTAOH pair gave an alpha-effect of 57, showing that the alpha-effect can play an important role in micellar systems. We further investigated the effectiveness of reactive counterion surfactants in decontaminating selected environmental solids that were spiked with 27 ppb fenitrothion. The solids were as follows: the clay mineral montmorillonite and SO-1 and S0-2 soils (obtained from the Canadian Certified Reference Materials Project). The reactive counterion surfactant solutions significantly enhanced the rate of fenitrothion degradation in the spiked solids over that obtained when the spiked solid was placed in contact with either 0.02 M KOH or water. The rate enhancements followed the order CTAOOH > CTAMINA approximately CTAOH > KOH > water. We conclude that reactive counterion surfactants, especially with alpha-nucleophiles, hold great potential in terms of remediating soils contaminated by toxic organophosphorus esters.

Monte Carlo simulations of the properties and structure of hexadecyltrimethylammonium chloride micelles of various shapes in aqueous-salt solutions

NASA Astrophysics Data System (ADS)

Burov, S. V.; Piotrovskaya, E. M.

2006-08-01

The thermodynamic and structural properties of spherical and cylindrical hexadecyltrimethylammonium chloride micelles in water and a solution of sodium benzoate were studied by the Monte Carlo method. The local densities of particles in the systems, orientations of benzoate ions, two-particle distribution functions, and the influence of sodium benzoate admixtures on the properties and structure of micellar solutions were studied.

Use of spectroscopic technique to develop a reagent for Mo(VI) utilizing micellar effects on complex formation

NASA Astrophysics Data System (ADS)

Taşcioğlu, Sülin; Kaki, E.; Taşcioğlu, Senay

2012-09-01

Ultraviolet and visible spectral properties of aqueous solutions of molybdenum(VI) (Mo), gallic acid (GA), Lalanine (Ala), and L-Phenylalanine (Phe), and of their binary and ternary solutions were investigated in the absence and presence of anionic, cationic, and nonionic surfactant micelles. Evaluation of the spectra in a comparative way revealed that both Ala and Phe form ternary complexes with Mo and GA. The formation of a quaternary complex between Mo, GA, Phe, and cetyltrimethylammonium bromide at pH 4.5 provided a reagent system with a strikingly high sensitivity (1.2•106 l/(mol•cm)) for use in the spectrophotometric determination of Mo. A mechanism of micellar effects was discussed in terms of the substrate molecular charge and hydrophobicity, and rationalized on the basis of the spectral data obtained above and below the isoelectric pH of the amino acids.

Fabrication of gold dot, ring, and corpuscle arrays from block copolymer templates via a simple modification of surface energy

NASA Astrophysics Data System (ADS)

Cho, Heesook; Choi, Sinho; Kim, Jin Young; Park, Soojin

2011-12-01

We demonstrate a simple method for tuning the morphologies of as-spun micellar thin films by modifying the surface energy of silicon substrates. When a polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer dissolved in o-xylene was spin-coated onto a PS-modified surface, a dimple-type structure consisting of a thick PS shell and P2VP core was obtained. Subsequently, when the films were immersed in metal precursor solutions at certain periods of time and followed by plasma treatment, metal individual dots in a ring-shaped structure, metal nanoring, and metal corpuscle arrays were fabricated, depending on the loading amount of metal precursors. In contrast, when PS-b-P2VP films cast onto silicon substrates with a native oxide were used as templates, only metal dotted arrays were obtained. The combination of micellar thin film and surface energy modification offers an effective way to fabricate various nanostructured metal or metal oxide films.We demonstrate a simple method for tuning the morphologies of as-spun micellar thin films by modifying the surface energy of silicon substrates. When a polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer dissolved in o-xylene was spin-coated onto a PS-modified surface, a dimple-type structure consisting of a thick PS shell and P2VP core was obtained. Subsequently, when the films were immersed in metal precursor solutions at certain periods of time and followed by plasma treatment, metal individual dots in a ring-shaped structure, metal nanoring, and metal corpuscle arrays were fabricated, depending on the loading amount of metal precursors. In contrast, when PS-b-P2VP films cast onto silicon substrates with a native oxide were used as templates, only metal dotted arrays were obtained. The combination of micellar thin film and surface energy modification offers an effective way to fabricate various nanostructured metal or metal oxide films. Electronic supplementary information (ESI) available: AFM images of Au nanorings prepared from a mixed solvent and characterization of PS-b-P2VP micellar films. See DOI: 10.1039/c1nr11075f

Ionization in liquids. Progress report, September 1, 1977-April 30, 1981

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakale, G.

1980-12-19

Quasifree electrons simulate the behavior of unsolvated or dry electrons in aqueous media including the special case of biological systems. A model of direct radiosensitization was developed based on dry charge-carriers having an extended lifetime in the sheath of structured water that surrounds polar biomolecules. In this model, the pre-solvation lifetimes of dry electrons increased with an increase in the rotational times of solvent molecules. During the development of this model, an increasing number of radiosensitizers were found to be carcinogenic. Measurement of the k/sub e/'s of known carcinogens and noncarcinogens revealed that carcinogens attached quasifree electrons at diffusion-controlled rates,more » whereas the k/sub e/'s of noncarcinogens were significantly less. To explore the k/sub e/-carcinogenicity correlation further, a study of quasifree electron attachment to the water pools of reversed micelles was conducted. The degree of structuredness of the water pools which determines the k/sub e/ of the reversed micellar systems was also controlled. Another approach to controlling the microenvironment of quasifree electrons in biological systems was done in studies of radiation-induced damage to DNA in concentrated DNA solutions. The high concentration of DNA introduces more structure into the solutions than that occurring in typical in vitro experiments. The structural enhancement by DNA extends the lifetime of unsolvated charge-carriers. The DNA-damaging effects of radiolyticaly produced charge-carriers were also determined in studies of synergistic mutagenesis in bacteria simultaneously exposed to ionizing radiation and electrophilic chemical carcinogens. The attachment-detachment equilibrium of nicotine in hexane solutions was also studied. Both the kinetics and the thermodynamics of electron reactions were studied. (ERB)« less

Separation and determination of peptide metabolite of Bacillus licheniformis in a microbial fuel cell by high-speed capillary micellar electrokinetic chromatography.

PubMed

Wang, Wei; Bai, Ruiguang; Cai, Xiaoyu; Lin, Ping; Ma, Lihong

2017-11-01

A method using high-speed capillary micellar electrokinetic chromatography and a microbial fuel cell was applied to determine the metabolite of the peptides released by Bacillus licheniformis. Two peptides, l-carnosine and l-alanyl-l-glutamine were used as the substrate to feed Bacillus licheniformis in a microbial fuel cell. The metabolism process of the bacterium was monitored by analyzing the voltage outputs of the microbial fuel cell. A home-made spontaneous injection device was applied to perform high-speed capillary micellar electrokinetic chromatography. Under the optimized conditions, tryptophan, glycine, valine, tyrosine and the two peptides could be rapidly separated within 2.5 min with micellar electrokinetic chromatography mode. Then the method was applied to analyze the solutions sampled from the microbial fuel cell. After 92 h running, valine, as the metabolite, was successfully detected with concentration 3.90 × 10 -5 M. The results demonstrated that Bacillus licheniformis could convert l-carnosine and l-alanyl-l-glutamine into valine. The method employed in this work was proved to have great potential in analysis of metabolites, such as amino acids, for microorganisms. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermodynamics of sodium dodecyl sulphate-salicylic acid based micellar systems and their potential use in fruits postharvest.

PubMed

Cid, A; Morales, J; Mejuto, J C; Briz-Cid, N; Rial-Otero, R; Simal-Gándara, J

2014-05-15

Micellar systems have excellent food applications due to their capability to solubilise a large range of hydrophilic and hydrophobic substances. In this work, the mixed micelle formation between the ionic surfactant sodium dodecyl sulphate (SDS) and the phenolic acid salicylic acid have been studied at several temperatures in aqueous solution. The critical micelle concentration and the micellization degree were determined by conductometric techniques and the experimental data used to calculate several useful thermodynamic parameters, like standard free energy, enthalpy and entropy of micelle formation. Salicylic acid helps the micellization of SDS, both by increasing the additive concentration at a constant temperature and by increasing temperature at a constant concentration of additive. The formation of micelles of SDS in the presence of salicylic acid was a thermodynamically spontaneous process, and is also entropically controlled. Salicylic acid plays the role of a stabilizer, and gives a pathway to control the three-dimensional water matrix structure. The driving force of the micellization process is provided by the hydrophobic interactions. The isostructural temperature was found to be 307.5 K for the mixed micellar system. This article explores the use of SDS-salicylic acid based micellar systems for their potential use in fruits postharvest. Copyright © 2013 Elsevier Ltd. All rights reserved.

Process optimization for reverse micellar extraction of stem bromelain with a focus on back extraction.

PubMed

Dhaneshwar, Amrut D; Chaurasiya, Ram Saran; Hebbar, H Umesh

2014-01-01

In the current study, reverse micellar extraction (RME) for the purification of stem bromelain was successfully achieved using the sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane system. A maximum forward extraction efficiency of 58.0% was obtained at 100 mM AOT concentration, aqueous phase pH of 8.0 and 0.2 M NaCl. Back extraction studies on altering stripping phase pH and KCl concentration, addition of counter-ion and iso-propyl alcohol (IPA) and mechanical agitation with glass beads indicated that IPA addition and agitation with glass beads have significant effects on extraction efficiency. The protein extraction was higher (51.9%) in case of the IPA (10% v/v) added system during back extraction as compared to a cetyltrimethylammonium bromide (100 mM) added system (9.42%). The central composite design technique was used to optimize the back extraction conditions further. Concentration of IPA, amount of glass beads, mixing time, and agitation speed (in rpm) were the variables selected. IPA concentration of 8.5% (v/v), glass bead concentration of 0.6 (w/v), and mixing time of 45 min at 400 rpm resulted in higher back extraction efficiency of 45.6% and activity recovery of 88.8% with purification of 3.04-fold. The study indicated that mechanical agitation using glass beads could be used for destabilizing the reverse micelles and release of bromelain back into the fresh aqueous phase. © 2014 American Institute of Chemical Engineers.

Solubilization of Therapeutic Agents in Micellar Nanomedicines

PubMed Central

Vuković, Lela; Madriaga, Antonett; Kuzmis, Antonina; Banerjee, Amrita; Tang, Alan; Tao, Kevin; Shah, Neil; Král, Petr; Onyuksel, Hayat

2014-01-01

We use atomistic molecular dynamics simulations to reveal the binding mechanisms of therapeutic agents in PEG-ylated micellar nanocarriers (SSM). In our experiments, SSM in buffer solutions can solubilize either ≈ 11 small bexarotene molecules or ≈ 6 (2 in low ionic strength buffer) human vasoactive intestinal peptide (VIP) molecules. Free energy calculations reveal that molecules of the poorly water soluble drug bexarotene can reside at the micellar ionic interface of the PEG corona, with their polar ends pointing out. Alternatively, they can reside in the alkane core center, where several bexarotene molecules can self-stabilize by forming a cluster held together by a network of hydrogen bonds. We also show that highly charged molecules, such as VIP, can be stabilized at the SSM ionic interface by Coulombic coupling between their positively charged residues and the negatively charged phosphate head-groups of the lipids. The obtained results illustrate that atomistic simulations can reveal drug solubilization character in nanocarriers and be used in efficient optimization of novel nanomedicines. PMID:24283508

Determination of patulin in commercial apple juice by micellar electrokinetic chromatography.

PubMed

Murillo, M; González-Peñas, E; Amézqueta, S

2008-01-01

A novel and validated micellar electrokinetic capillary chromatography (MEKC) method using ultraviolet detection (UV) has been applied to the quantitative analysis of patulin (PAT) in commercial apple juice. Patulin was extracted from samples with an ethylacetate solution. The micellar electrokinetic capillary chromatography (MECK) parameters studied for method optimization were buffer composition, voltage, temperature, and a separation between PAT and 5-hydroxymethylfurfural (HMF) (main interference in apple juice PAT analysis) peaks until reaching baseline. The method passes a series of validation tests including selectivity, linearity, limit of detection and quantification (0.7 and 2.5 microgL(-1), respectively), precision (within and between-day variability) and recovery (80.2% RSD=4%), accuracy, and robustness. This method was successfully applied to the measurement of 20 apple juice samples obtained from different supermarkets. One hundred percent of the samples were contaminated with a level greater than the limit of detection, with mean and median values of 41.3 and 35.7 microgL(-1), respectively.

Solubilisation of poorly water-soluble drugs during in vitro lipolysis of medium- and long-chain triacylglycerols.

PubMed

Christensen, Janne Ørskov; Schultz, Kirsten; Mollgaard, Birgitte; Kristensen, Henning Gjelstrup; Mullertz, Anette

2004-11-01

The partitioning of poorly soluble drugs into an aqueous micellar phase was exploited using an in vitro lipid digestion model, simulating the events taking place during digestion of acylglycerols in the duodenum. The aqueous micellar phase was isolated after ultracentrifugation of samples obtained at different degrees of triacylglycerol hydrolysis. Flupentixol, 1'-[4-[1-(4-fluorophenyl)-1-H-indol-3-yl]-1-butyl]spiro[iso-benzofuran-1(3H), 4' piperidine] (LU 28-179) and probucol were studied. The effect of the alkyl chain length of the triacylglycerol was studied using a medium-chain triacylglycerol (MCT) and a long-chain triacylglycerol (LCT), respectively. In general, an oil solution was used as the lipid source in the model. Samples were analysed in regard to micellar size, lipid composition and drug concentration. During lipolysis, the content of lipolytic products in the aqueous micellar phase increased. The micellar size (R(H) approximately 3 nm) only increased when long-chain lipolytic products were incorporated in the mixed micelles (R(H) approximately 7.8 nm). Flupentixol was quickly transferred to the mixed micelles due to high solubility in this phase (100% released). A tendency towards higher solubilisation of LU 28-179, when it was administered in the LCT (approximately 24% released) compared to when it was administered in the MCT (approximately 15% released) at 70% hydrolysis, and a lagphase was observed. There was no difference in the solubilisation of probucol using MCT or LCT ( approximately 20% released), respectively. Differences in the physicochemical properties of the drugs resulted in differences in their distribution between the phases arising during lipolysis.

Thermosetting microemulsions and mixed micellar solutions as drug delivery systems for periodontal anesthesia.

PubMed

Scherlund, M; Malmsten, M; Holmqvist, P; Brodin, A

2000-01-20

In the present study, thermosetting microemulsions and mixed micellar solutions were investigated as drug delivery systems for anesthetizing the periodontal pocket. The structure of the systems, consisting of the active ingredients lidocaine and prilocaine, as well as two block copolymers (Lutrol F127 and Lutrol F68), was investigated by NMR spectroscopy and photon correlation spectroscopy (PCS). The results obtained for dilute (1-3% w/w) solutions show discrete micelles with a diameter of 20-30 nm and a critical micellization temperature of 25-35 degrees C. Gel permeation chromatography (GPC) was used to study the distribution of the active ingredients, and indicates a preferential solubilization of the active components in micelles over unimers. Analogous to the Lutrol F127 single component system these formulations display an abrupt gelation on increasing temperature. The gelation temperature was found to depend on both the drug ionization and concentration. These systems have several advantages over emulsion-based formulations including good stability, ease of preparation, increased drug release rate, and improved handling due to the transparency of the formulations.

Wormlike micelle formation by acylglutamic acid with alkylamines.

PubMed

Sakai, Kenichi; Nomura, Kazuyuki; Shrestha, Rekha Goswami; Endo, Takeshi; Sakamoto, Kazutami; Sakai, Hideki; Abe, Masahiko

2012-12-21

Rheological properties of alkyl dicarboxylic acid-alkylamine complex systems have been characterized. The complex materials employed in this study consist of an amino acid-based surfactant (dodecanoylglutamic acid, C12Glu) and a tertiary alkylamine (dodecyldimethylamine, C12DMA) or a secondary alkylamine (dodecylmethylamine, C12MA). (1)H NMR and mass spectroscopic data have suggested that C12Glu forms a stoichiometric 1:1 complex with C12DMA and C12MA. Rheological measurements have suggested that the complex systems yield viscoelastic wormlike micellar solutions and the rheological behavior is strongly dependent on the aqueous solution pH. This pH-dependent behavior results from the structural transformation of the wormlike micelles to occur in the narrow pH range 5.5-6.2 (in the case of C12Glu-C12DMA system); i.e., positive curved aggregates such as spherical or rodlike micelles tend to be formed at high pH values. Our current study offers a unique way to obtain viscoelastic wormlike micellar solutions by means of alkyl dicarboxylic acid-alkylamine complex as gemini-like amphiphiles.

A dispersive liquid-liquid micellar microextraction for the determination of pharmaceutical compounds in wastewaters using ultra-high-performace liquid chromatography with DAD detection.

PubMed

Montesdeoca-Esponda, Sarah; Mahugo-Santana, Cristina; Sosa-Ferrera, Zoraida; Santana-Rodríguez, José Juan

2015-03-01

A dispersive liquid-liquid micellar microextraction (DLLMME) method coupled with ultra-high-performance liquid chromatography (UHPLC) using Diode Array Detector (DAD) detector was developed for the analysis of five pharmaceutical compounds of different nature in wastewaters. A micellar solution of a surfactant, polidocanol, as extraction solvent (100 μL) and chloroform as dispersive solvent (200 μL) were used to extract and preconcentrate the target analytes. Samples were heated above critical temperature and the cloudy solution was centrifuged. After removing the chloroform, the reduced volume of surfactant was then injected in the UHPLC system. In order to obtain high extraction efficiency, the parameters affecting the liquid-phase microextraction, such as time and temperature extraction, ionic strength and surfactant and organic solvent volume, were optimized using an experimental design. Under the optimized conditions, this procedure allows enrichment factors of up to 47-fold. The detection limit of the method ranged from 0.1 to 2.0 µg/L for the different pharmaceuticals. Relative standard deviations were <26% for all compounds. The procedure was applied to samples from final effluent collected from wastewater treatment plants in Las Palmas de Gran Canaria (Spain), and two compounds were measured at 67 and 113 µg/L in one of them. Copyright © 2014 John Wiley & Sons, Ltd.

Dissolution and solubility behavior of fenofibrate in sodium lauryl sulfate solutions.

PubMed

Granero, Gladys E; Ramachandran, Chandrasekharan; Amidon, Gordon L

2005-10-01

The solubility of fenofibrate in pH 6.8 McIlvaine buffers containing varying concentrations of sodium lauryl sulfate was determined. The dissolution behavior of fenofibrate was also examined in the same solutions with rotating disk experiments. It was observed that the enhancement in intrinsic dissolution rate was approximately 500-fold and the enhancement in solubility was approximately 2000-fold in a pH 6.8 buffer containing 2% (w/v) sodium lauryl sulfate compared to that in buffer alone. The micellar solubilization equilibrium coefficient (k*) was estimated from the solubility data and found to be 30884+/-213 L/mol. The diffusivity for the free solute, 7.15x10(-6) cm2/s, was calculated using Schroeder's additive molal volume estimates and Hayduk-Laurie correlation. The diffusivity of the drug-loaded micelle, estimated from the experimental solubility and dissolution data and the calculated value for free solute diffusivity, was 0.86x10(-6) cm2/s. Thus, the much lower enhancement in dissolution of fenofibrate compared to its enhancement in solubility in surfactant solutions appears to be consistent with the contribution to the total transport due to enhanced micellar solubilization as well as a large decrease (approximately 8-fold) in the diffusivity of the drug-loaded micelle.

Self-assembling colloidal system for the ocular administration of cyclosporine A.

PubMed

Luschmann, Christoph; Tessmar, Joerg; Schoeberl, Simon; Strauß, Olaf; Luschmann, Karl; Goepferich, Achim

2014-01-01

In this study, we developed a self-assembling micellar system to deliver cyclosporine A (CsA) in an aqueous solution to the cornea. Two nonionic surfactants of the poly(ethylene glycol)-fatty alcohol ether type (Sympatens AS and Sympatens ACS) were characterized in terms of micelle size, shape, and charge, and their encapsulation efficiency for CsA. In an in situ single dose bioavailability study, the corneal CsA levels were determined in an enucleated porcine eye model. A commercial formulation and a 2% CsA olive oil solution served as references. Both surfactants formed spherical micelles with a size of 9 to 12 nm in water. A concentration as low as 0.3% (wt/vol) Sympatens AS was sufficient to entrap therapeutic levels of at least 0.1% (wt/vol) CsA. In the porcine in situ model, exceptionally high drug levels in the cornea were obtained for the micellar CsA solution (1557 ± 407 ngCsA/gcornea). They were significantly higher than those of Restasis (545 ± 137 ngCsA/gcornea) or the olive oil solution (452 ± 142 ngCsA/gcornea). In conclusion, we have shown a promising simple and efficient approach for the application of CsA in an aqueous solution to the cornea to treat inflammatory corneal diseases.

1H, 13C and 15N assignment of the C-terminal domain of GNA2132 from Neisseria meningitidis.

PubMed

Esposito, Veronica; Musi, Valeria; Veggi, Daniele; Pastore, Annalisa; Pizza, Mariagrazia

2010-04-01

GNA2132 (Genome-derived Neisseria Antigen 2132) is a surface-exposed lipoprotein discovered by reverse vaccinology and expressed by genetically diverse Neisseria meningitidis strains (Pizza et al. 2000). The protein induces bactericidal antibodies against most strains of Meningococccus and has been included in a multivalent recombinant vaccine against N. meningitidis serogroup B. Structure determination of GNA2132 is important for understanding the antigenic properties of the protein in view of increased efficiency vaccine development. We report practically complete (1)H, (13)C and (15)N assignment of the detectable spectrum of a highly conserved C-terminal region of GNA2132 (residues 245-427) in micellar solution, a medium used to improve the spectral quality. The first 32 residues of our construct up to residue 277 were not visible in the spectrum, presumably because of line broadening due to solvent and/or conformational exchange. Secondary structure predictions based on chemical shift information indicate the presence of an all beta-protein with eight beta strands.

Light-Induced Gelling in a Micellar Fluid Based on a Zwitterionic Surfactant.

NASA Astrophysics Data System (ADS)

Kumar, Rakesh; Raghavan, Srinivasa

2007-03-01

Fluids with photoresponsive rheological properties (i.e. photorheological or PR fluids) can be useful in a range of applications, such as in dampers, sensors, and valves for microfluidic or MEMS devices. Previously, we have demonstrated a cationic surfactant-based PR fluid whose viscosity can be rapidly decreased by UV irradiation. This viscosity decrease was not reversible. Here, we describe a different formulation based on a zwitterionic surfactant that shows a rapid increase in viscosity (gelling) upon exposure to UV radiation. The formulation consists of the zwitterionic surfactant and a photosensitive cinnamic acid derivative. Initially, the viscosity of the fluid is low indicating the presence of small micelles. Upon UV irradiation, the cinnamic acid derivative is photoisomerized from trans to cis. In turn, the small micelles transform into long wormlike micelles, thus increasing the solution viscosity by more than five orders of magnitude. Small angle neutron scattering (SANS) data confirms the dramatic increase in micelle length. Possible reasons for such changes in micelle dimensions will be discussed.

Solubilization of flurbiprofen within non-ionic Tween 20 surfactant micelles: a 19F and 1H NMR study.

PubMed

Saveyn, Pieter; Cocquyt, Ellen; Zhu, Wuxin; Sinnaeve, Davy; Haustraete, Katrien; Martins, José C; Van der Meeren, Paul

2009-07-14

The solubilization of the poorly water soluble anti-inflammatory drug flurbiprofen in non-ionic Tween 20 surfactant micellar solutions was studied by both (19)F and (1)H NMR spectroscopy in an acidic environment. These non-destructive techniques allowed us to investigate the effect of temperature cycling in situ. Using (19)F NMR, an increased solubilisation capacity was observed as the temperature increased. This effect became more pronounced above the cloud point, which was reduced by more than 30 degrees C in the presence of an excess of flurbiprofen. Upon clouding, peak splitting was observed in the (19)F spectrum, which indicates that two pools of solubilised flurbiprofen exist that are in slow exchange on the NMR frequency timescale. The clouding and solubilization processes were found to be reversible, albeit with slow kinetics. Based on chemical shift differences of both Tween 20 and flurbiprofen, as well as NOESY experiments, the flurbiprofen was found to be accumulated within the palisade layer of the Tween 20 micelles.

Amphiphilic invertible polymers: Self-assembly into functional materials driven by environment polarity

NASA Astrophysics Data System (ADS)

Hevus, Ivan

Stimuli-responsive polymers adapt to environmental changes by adjusting their chain conformation in a fast and reversible way. Responsive polymeric materials have already found use in electronics, coatings industry, personal care, and bio-related areas. The current work aims at the development of novel responsive functional polymeric materials by manipulating environment-dependent self-assembly of a new class of responsive macromolecules strategically designed in this study,—amphiphilic invertible polymers (AIPs). Environment-dependent micellization and self-assembly of three different synthesized AIP types based on poly(ethylene glycol) as a hydrophilic fragment and varying hydrophobic constituents was demonstrated in polar and nonpolar solvents, as well as on the surfaces and interfaces. With increasing concentration, AIP micelles self-assemble into invertible micellar assemblies composed of hydrophilic and hydrophobic domains. Polarity-responsive properties of AIPs make invertible micellar assemblies functional in polar and nonpolar media including at interfaces. Thus, invertible micellar assemblies solubilize poorly soluble substances in their interior in polar and nonpolar solvents. In a polar aqueous medium, a novel stimuli-responsive mechanism of drug release based on response of AIP-based drug delivery system to polarity change upon contact with the target cell has been established using invertible micellar assemblies loaded with curcumin, a phytochemical drug. In a nonpolar medium, invertible micellar assemblies were applied simultaneously as nanoreactors and stabilizers for size-controlled synthesis of silver nanoparticles stable in both polar and nonpolar media. The developed amphiphilic nanosilver was subsequently used as seeds to promote anisotropic growth of CdSe semiconductor nanoparticles that have potential in different applications ranging from physics to medicine. Amphiphilic invertible polymers were shown to adsorb on the surface of silica nanoparticles strongly differing in polarity. AIP modified silica nanoparticles are able to adsolubilize molecules of poorly water-soluble 2-naphthol into the adsorbed polymer layer. The adsolubilization ability of adsorbed invertible macromolecules makes AIP-modified silica nanoparticles potentially useful in wastewater treatment or biomedical applications. Finally, the invertible micellar assemblies were used as functional additives to improve the appearance of electrospun silicon wires based on cyclohexasilane, a liquid silicon precursor. AIP-assisted fabrication of silicon wires from the liquid cyclohexasilane precursor has potential as a scalable method for developing electronic functional materials.

Picosecond to nanosecond reorganization of water in AOT/lecithin mixed reverse micelles of different morphology

NASA Astrophysics Data System (ADS)

Narayanan, S. Shankara; Sinha, Sudarson Sekhar; Sarkar, Rupa; Pal, Samir Kumar

2008-02-01

We report the effect of different geometrical restrictions on the dynamical properties of water using dynamic light scattering (DLS), Fourier transform infrared (FTIR) and picosecond-resolved fluorescence studies. By preparing AOT/lecithin mixed reverse micelles (RMs) of different morphologies (spherical and ellipsoidal), we have investigated the effect of the degree of confinement on the mobility of water in the mixed RMs of similar degree of hydration. The FTIR studies along with solvation dynamics of two fluorescent probes, ANS and coumarin 500 in the RMs reveal structural and dynamical information about the micellar water, which varies with the morphology of the mixed RMs.

Interactions in micellar solutions of β-casein

NASA Astrophysics Data System (ADS)

Leclerc, E.; Calmettes, P.

1997-02-01

β-casein is a protein which forms micelles in aqueous solvents. The magnitude and the range of the weight-average interactions between the diverse solute particles are infrared from small-angle neutron scattering measurements made on various β-casein solutions. Well above the critical micelle concentration (CMC), these interactions are repulsive. They weaken with decreasing protein concentration, and finally become strongly attractive near the CMC. Although indispensable for micelle formation this fact has never been reported so far.

Studies of bio-mimetic medium of ionic and non-ionic micelles by a simple charge transfer fluorescence probe N,N-dimethylaminonapthyl-(acrylo)-nitrile

NASA Astrophysics Data System (ADS)

Samanta, Anuva; Paul, Bijan Kumar; Guchhait, N.

2011-05-01

In this report we have studied micellization process of anionic, cationic and non-ionic surfactants using N,N-dimethylaminonapthyl-(acrylo)-nitrile (DMANAN) as an external fluorescence probe. Micropolarity, microviscosity, critical micellar concentration of these micelles based on steady state absorption and fluorescence and time resolved emission spectroscopy of the probe DMANAN show that the molecule resides in the micelle-water interface for ionic micelles and in the core for the non-ionic micelle. The effect of variation of pH of the micellar solution as well as fluorescence quenching measurements of DMANAN provide further support for the location of the probe in the micelles.

Large PAMAM Dendron Induces Formation of Unusual P4332 Mesophase in Monoolein/Water system.

PubMed

Kumar, Manoj; Patil, Naganath G; Ambade, Ashootosh V; Kumaraswamy, Guruswamy

2018-05-18

Compact macromolecular dendrons have been shown to induce the formation of discontinuous inverse micellar assemblies with Fd3m symmetry in monoolein/water systems. Here, we demonstrate that a large PAMAM dendron (G5: fifth generation) induces the formation a very unusual mesophase with P4332 symmetry. This mesophase had previously been observed in monoolein/water systems only on addition of cytochrome C. The P4332 mesophase can be considered an intermediate phase between the bicontinuous Ia3d and discontinuous micellar mesophases. In this unusual phase, every third rod junction of the Ia3d mesophase is replaced with a spherical micelle. We present a detailed investigation of the phase behaviour of monoolein/water as a function of G5 concentration and temperature. Addition of 1% G5 in 85/15 monoolein/water system induces a transition from the L to Ia3d phase. Further increase in G5 concentration to above 2% induces the formation of the P4332 phase. Thus, incorporation of G5 yields a qualitatively different phase diagram when compared with incorporation of lower generation PAMAM dendrons (G2 - G4) in monoolein/water, where the reverse micellar Fd3m phase forms. PAMAM dendrons of all generations, G2 - G5, bear terminal amine groups that interact with the monoolein head group. The compact molecular architecture of the dendrons and these attractive interactions induce bending of the monoolein bilayer structure. For smaller dendrons, G2 - G4, this results in the formation of the Fd3m phase. However, the large size of the G5 dendron precludes this and a rare intermediate phase between the Ia3d and discontinuous micellar phase, the P4332 mesophase forms instead.

Mixtures of lecithin and bile salt can form highly viscous wormlike micellar solutions in water.

PubMed

Cheng, Chih-Yang; Oh, Hyuntaek; Wang, Ting-Yu; Raghavan, Srinivasa R; Tung, Shih-Huang

2014-09-02

The self-assembly of biological surfactants in water is an important topic for study because of its relevance to physiological processes. Two common types of biosurfactants are lecithin (phosphatidylcholine) and bile salts, which are both present in bile and involved in digestion. Previous studies on lecithin-bile salt mixtures have reported the formation of short, rodlike micelles. Here, we show that lecithin-bile salt micelles can be further induced to grow into long, flexible wormlike structures. The formation of long worms and their resultant entanglement into transient networks is reflected in the rheology: the fluids become viscoelastic and exhibit Maxwellian behavior, and their zero-shear viscosity can be up to a 1000-fold higher than that of water. The presence of worms is further confirmed by data from small-angle neutron and X-ray scattering and from cryo-transmission electron microscopy (cryo-TEM). We find that micellar growth peaks at a specific molar ratio (near equimolar) of bile salt:lecithin, which suggests a strong binding interaction between the two species. In addition, micellar growth also requires a sufficient concentration of background electrolyte such as NaCl or sodium citrate that serves to screen the electrostatic repulsion of the amphiphiles and to "salt out" the amphiphiles. We postulate a mechanism based on changes in the molecular geometry caused by bile salts and electrolytes to explain the micellar growth.

Retention of bile salts in micellar electrokinetic chromatography: relation of capacity factor to octanol-water partition coefficient and critical micellar concentration.

PubMed

Lucangioli, S E; Carducci, C N; Tripodi, V P; Kenndler, E

2001-12-25

The capacity factors of 16 anionic cholates (from six bile salts, including their glyco- and tauro-conjugates) were determined in a micellar electrokinetic chromatography (MEKC) system consisting of buffer, pH 7.5 (phosphate-boric acid; 20 mmol/l) with 50 mmol/l sodium dodecyl sulfate (SDS) as micelle former and 10% acetonitrile as organic modifier. The capacity factors of the fully dissociated, negatively charged analytes (ranging between 0.2 and 60) were calculated from their mobilities, with a reference background electrolyte (BGE) without SDS representing "free" solution. For comparison, the capacity factors were derived for a second reference BGE where the SDS concentration (5 mmol/l) is close to the critical micellar concentration (CMC). The capacity factors are compared with the logarithm of the octanol-water partition coefficient, log Pow, as measure for lipophilicity. Clear disagreement between these two parameters is found especially for epimeric cholates with the hydroxy group in position 7. In contrast, fair relation between the capacity factor of the analytes and their CMC is observed both depending strongly on the orientation of the OH groups, and tauro-conjugation as well. In this respect the retention behaviour of the bile salts in MEKC seems to reflect their role as detergents in living systems, and might serve as model parameter beyond lipophilicity.

Can neutral analytes be concentrated by transient isotachophoresis in micellar electrokinetic chromatography and how much?

PubMed

Matczuk, Magdalena; Foteeva, Lidia S; Jarosz, Maciej; Galanski, Markus; Keppler, Bernhard K; Hirokawa, Takeshi; Timerbaev, Andrei R

2014-06-06

Transient isotachophoresis (tITP) is a versatile sample preconcentration technique that uses ITP to focus electrically charged analytes at the initial stage of CE analysis. However, according to the ruling principle of tITP, uncharged analytes are beyond its capacity while being separated and detected by micellar electrokinetic chromatography (MEKC). On the other hand, when these are charged micelles that undergo the tITP focusing, one can anticipate the concentration effect, resulting from the formation of transient micellar stack at moving sample/background electrolyte (BGE) boundary, which increasingly accumulates the analytes. This work expands the enrichment potential of tITP for MEKC by demonstrating the quantitative analysis of uncharged metal-based drugs from highly saline samples and introducing to the BGE solution anionic surfactants and buffer (terminating) co-ions of different mobility and concentration to optimize performance. Metallodrugs of assorted lipophilicity were chosen so as to explore whether their varying affinity toward micelles plays the role. In addition to altering the sample and BGE composition, optimization of the detection capability was achieved due to fine-tuning operational variables such as sample volume, separation voltage and pressure, etc. The results of optimization trials shed light on the mechanism of micellar tITP and render effective determination of selected drugs in human urine, with practical limits of detection using conventional UV detector. Copyright © 2014 Elsevier B.V. All rights reserved.

Reverse micellar extraction of bromelain from pineapple peel--Effect of surfactant structure.

PubMed

Wan, Jing; Guo, Jingjing; Miao, Zhitong; Guo, Xia

2016-04-15

Pineapple peel is generally disposed or used as compost. This study was focused on extracting bromelain from pineapple peel by using reverse micelles. It was found that gemini surfactant C12-8-C12·2Br (octamethylene-α,ω-bis(dimethyldodecylammonium bromide)) showed distinctive advantage over its monomeric counterpart DTAB (dodecyl trimethyl ammonium bromide); under optimized condition, the bromelain extracted with C12-8-C12·2Br reverse micelle had an activity recovery of 163% and a purification fold of 3.3, while when using DTAB reverse micelle, the activity recovery was 95% and the purification fold was 1.7. Therefore, the spacer of gemini surfactant should play a positive role in bromelain extraction and may suggest the potential of gemini surfactant in protein separation since it has been so far rarely used in relative experiments or technologies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Validation and divergence of the activation energy barrier crossing transition at the AOT/lecithin reverse micellar interface.

PubMed

Narayanan, S Shankara; Sinha, Sudarson Sekhar; Sarkar, Rupa; Pal, Samir Kumar

2008-03-13

In this report, the validity and divergence of the activation energy barrier crossing model for the bound to free type water transition at the interface of the AOT/lecithin mixed reverse micelle (RM) has been investigated for the first time in a wide range of temperatures by time-resolved solvation of fluorophores. Here, picosecond-resolved solvation dynamics of two fluorescent probes, ANS (1-anilino-8-naphthalenesulfonic acid, ammonium salt) and Coumarin 500 (C-500), in the mixed RM have been carefully examined at 293, 313, 328, and 343 K. Using the dynamic light scattering (DLS) technique, the size of the mixed RMs at different temperatures was found to have an insignificant change. The solvation process at the reverse micellar interface has been found to be the activation energy barrier crossing type, in which interface-bound type water molecules get converted into free type water molecules. The activation energies, Ea, calculated for ANS and C-500 are 7.4 and 3.9 kcal mol(-1), respectively, which are in good agreement with that obtained by molecular dynamics simulation studies. However, deviation from the regular Arrhenius type behavior was observed for ANS around 343 K, which has been attributed to the spatial heterogeneity of the probe environments. Time-resolved fluorescence anisotropy decay of the probes has indicated the existence of the dyes in a range of locations in RM. With the increase in temperature, the overall anisotropy decay becomes faster revealing the lability of the microenvironment at elevated temperatures.

Citral degradation in micellar structures formed with polyoxyethylene-type surfactants.

PubMed

Park, Sung Joon; Hong, Chi Rac; Choi, Seung Jun

2015-03-01

In a micellar solution, the chemical degradation of poorly water-soluble food flavours can be influenced by the properties of the surfactants forming the micelles in aqueous solutions. To evaluate how hydrophilic head size and hydrophobic tail length influence the chemical degradation rate of food flavour, micelles were prepared with Brij surfactants (Brij 35, 58, 78 and 700), each of which had very similar molecular structures (polyoxyethylene fatty acid ether). The chemical degradation of citral in Brij micelles was found to be highest in an acidic environment. There was no significant difference in the chemical degradation rate of citral in Brij micelles in non-acidic conditions, regardless of the hydrophilic head size or hydrophobic tail length. Brij surfactants with larger hydrophilic heads effectively retarded the chemical degradation of citral in an acidic environment. Our findings suggest that the length of the hydrophobic tail rarely influenced the micelle's ability to chemically stabilize citral. Copyright © 2014 Elsevier Ltd. All rights reserved.

Excitation energy transfer in europium chelate with doxycycline in the presence of a second ligand in micellar solutions of nonionic surfactants

NASA Astrophysics Data System (ADS)

Smirnova, T. D.; Shtykov, S. N.; Kochubei, V. I.; Khryachkova, E. S.

2011-01-01

The complexation of Eu3+ with doxycycline (DC) antibiotic in the presence of several second ligands and surfactant micelles of different types is studied by the spectrophotometric and luminescence methods. It is found that the efficiency of excitation energy transfer in Eu3+-DC chelate depends on the nature of the second ligand and surfactant micelles. Using thenoyltrifluoroacetone (TTA) as an example, it is shown that the second ligand additionally sensitizes the europium fluorescence, and the possibility of intermediate sensitization of DC and then of europium is shown by the example of 1,10-phenanthroline. In all cases, the excitation energy transfer efficiency was increased due to the so-called antenna effect. The decay kinetics of the sensitized fluorescence of the binary and mixed-ligand chelates in aqueous and micellar solutions of nonionic surfactants is studied and the relative quantum yields and lifetimes of fluorescence are determined.

Layering Transitions and Squeeze-Out Patterns in Nanoscale Polymeric Soap Films

NASA Astrophysics Data System (ADS)

Berg, Steffen; Troian, Sandra M.

2004-11-01

Oscillatory forces in freely suspended or confined nanofilms of micellar solutions, colloidal suspensions, alkanes and semidilute polyelectrolyte films generate stepwise thinning during the final stages of film drainage. The step jump correlates with the basic aggregation unit such as the micellar size or the polymer mesh size. In all studies so far reported, the interface separating films of different thickness is circular or elliptical, as seen in common or Newton black films. Our studies of freely suspended soaps films containing an anionic surfactant and nonionic polymer have revealed that the last stratification event expands with a fractal boundary whose dimension increases with the solution viscosity above a critical value. Unstable front propagation resembles a viscous fingering instability. We propose that internal film layering due to confinement of polymer-surfactant aggregates leads to a smaller viscosity in the thinnest film (≈ 12 nm), which rapidly penetrates into an exterior layer (≈ 62 nm) of higher viscosity. Subsequent coarsening of the fractal interface mimics shapes recently observed in macroscopic systems.

Microstructure and Rheology of a Flow-Induced Structured Phase in Wormlike Micellar Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardiel Rivera, Joshua J.; Dohnalkova, Alice; Dubash, Neville

2013-04-30

Surfactant molecules found in soaps and detergents can self-assemble into a great variety of morphologies (e.g., spherical micelles, cylindrical micelles, and lamellar phases). The resulting morphology is highly affected by ionic strength, temperature, and flow conditions. In particular, cylindrical micelles in the presence of inorganic or organic salts can self-assemble into large flexible and elongated wormlike micelles. In equilibrium, the wormlike micelles transition from slightly entangled to branched and, finally, to multi-connected structures with increasing salt concentration. In our work, by introducing external flow conditions via microfluidics, these micellar structures can follow very different trajectories on the phase map andmore » new nanoporous structures can be created. This flow induced approach offers great potential to create novel materials and nanoporous scaffolds from wormlike micelles under ambient temperature and pressure, without any chemical and thermal means (1). As a result, this work provides attractive solutions for synthesizing new biocompatible materials under ambient conditions with biosensing, encapsulation, catalysis, photonics, and self-healing applications.« less

Interactions in Micellar Solutions of β-Casein

NASA Astrophysics Data System (ADS)

Leclerc, E.; Calmettes, P.

1997-01-01

β-casein is a flexible amphiphilic milk protein which forms spherical micelles in very dilute solution. The magnitude of the weight-average interactions between the solute particles has been inferred from small-angle neutron scattering experiments. At relatively high protein concentrations the interactions between micelles are repulsive, whatever the temperature. At lower concentration these interactions vanish and become more and more attractive when the critical micelle concentration is approached. Although indispensable for micelle formation, this fact seems to have not been previously reported.

Effect of the interaction of heat-processing style and fat type on the micellarization of lipid-soluble pigments from green and red pungent peppers (Capsicum annuum).

PubMed

Victoria-Campos, Claudia I; Ornelas-Paz, José de Jesús; Yahia, Elhadi M; Failla, Mark L

2013-04-17

The high diversity of carotenoids and chlorophylls in foods contrasts with the reduced number of pigments that typically are investigated in micellarization studies. In this study, pepper samples (raw and heat-treated) contained 68 individual pigments, but only 38 of them were micellarized after in vitro digestion. The micellarization of pigments was majorly determined by the interaction effect of processing style (food matrix effect) and fat type (saturated and unsaturated). The highest micellarization was observed with raw peppers. Unsaturated fat increased the micellarization of carotenoid esters, while the impact of fat on the micellarization of free carotenoids seemed to be dependent on pigment structure. The micellarization efficiency was diminished as the esterification level of carotenoids increased. The type of fatty acid moiety and the polarity of the carotenoids modulated their micellarization. Chlorophylls were transformed into pheophytins by heat-processing and digestion, with the pheophytins being stable under gastrointestinal conditions. Micellarization of pheophytins was improved by fat.

Phase separation in solution of worm-like micelles: a dilute ? spin-vector model

NASA Astrophysics Data System (ADS)

Panizza, Pascal; Cristobal, Galder; Curély, Jacques

1998-12-01

We show how the dilute 0953-8984/10/50/006/img2 spin vector model introduced originally by Wheeler and co-workers for describing the polymerization phenomenon in solutions of liquid sulphur and of living polymers may be conveniently adapted for studying phase separation in systems containing long flexible micelles. We draw an isomorphism between the coupling constant appearing in the exchange Hamiltonian and the surfactant energies in the micellar problem. We solve this problem within the mean-field approximation and compare the main results we have obtained with respect to polymer theory and previous theories of phase separation in micellar solutions. We show that the attractive interaction term 0953-8984/10/50/006/img3 between monomers renormalizes the aggregation energy and subsequently the corresponding size distribution. Under these conditions, we observe that the general aspect of the phase diagram in the 0953-8984/10/50/006/img4 plane (where 0953-8984/10/50/006/img5 is the surfactant concentration) is different from previous results. The spinodal line shows a re-entrant behaviour and, at low concentrations, we point out the possibility of specific nucleation phenomena related to the existence of a metastable transition line between a region composed of spherical micelles and another one corresponding to a dilute solution of long flexible micelles.

The use of micellar solutions for novel separation techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, Bruce Lynn

1993-01-01

Surfactant based separation techniques based on the solubilization of organic compounds into the nonpolar interior of a micelle or electrostatic attraction of ionized metals and metal complexes to the charged surface of a micelle were studied in this work. Micellar solutions were used to recover two model volatile organic compounds emitted by the printing and painting industries (toluene and amyl acetate) and to investigate the effect of the most important variables in the surfactant enhanced carbon regeneration (SECR) process. SECR for liquid phase applications was also investigated in which the equilibrium adsorption of cetyl pyridinium chloride (CPC) and sodium dodecylmore » sulfate (SDS) on activated carbon were measured. Micellar-enhanced ultrafiltration (MEUF) was investigated using spiral wound membranes for the simultaneous removal of organic compounds, metals and metal complexes dissolved in water, with emphasis on pollution control applications. Investigations of MEUF to remove 99+ per cent of trichloroethylene (TCE) from contaminated groundwater using criteria such as: membrane flux, solubilization equilibrium constant, surfactant molecular weight, and Krafft temperature led to the selection of an anionic disulfonate with a molecular weight of 642 (DOWFAX 8390). These data and results from supporting experiments were used to design a system which could clean-up water in a 100,000 gallon/day operation. A four stage process was found to be an effective design and estimated cost for such an operation were found to be in the range of the cost of mature competitive technologies.« less

Stable curcumin-loaded polymeric micellar formulation for enhancing cellular uptake and cytotoxicity to FLT3 overexpressing EoL-1 leukemic cells.

PubMed

Tima, Singkome; Anuchapreeda, Songyot; Ampasavate, Chadarat; Berkland, Cory; Okonogi, Siriporn

2017-05-01

The present study aims to develop a stable polymeric micellar formulation of curcumin (CM) with improved solubility and stability, and that is suitable for clinical applications in leukemia patients. CM-loaded polymeric micelles (CM-micelles) were prepared using poloxamers. The chemical structure of the polymers influenced micellar properties. The best formulation of CM-micelles, namely CM-P407, was obtained from poloxamer 407 at drug to polymer ratio of 1:30 and rehydrated with phosphate buffer solution pH 7.4. CM-P407 exhibited the smallest size of 30.3±1.3nm and highest entrapment efficiency of 88.4±4.1%. When stored at -80°C for 60days, CM-P407 retained high protection of CM and had no significant size change. In comparison with CM solution in dimethyl sulfoxide (CM-DMSO), CM kinetic degradation in both formulations followed a pseudo-first-order reaction, but the half-life of CM in CM-P407 was approx. 200 times longer than in CM-DMSO. Regarding the activity against FLT3 overexpressing EoL-1 leukemic cells, CM-P407 showed higher cytotoxicity than CM-DMSO. Moreover, intracellular uptake to leukemic cells of CM-P407 was 2-3 times greater than that of CM-DMSO. These promising results for CM-P407 will be further investigated in rodents and in clinical studies for leukemia treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Use of biopartitioning micellar chromatography and RP-HPLC for the determination of blood-brain barrier penetration of α-adrenergic/imidazoline receptor ligands, and QSPR analysis.

PubMed

Vucicevic, J; Popovic, M; Nikolic, K; Filipic, S; Obradovic, D; Agbaba, D

2017-03-01

For this study, 31 compounds, including 16 imidazoline/α-adrenergic receptor (IRs/α-ARs) ligands and 15 central nervous system (CNS) drugs, were characterized in terms of the retention factors (k) obtained using biopartitioning micellar and classical reversed phase chromatography (log k BMC and log k wRP , respectively). Based on the retention factor (log k wRP ) and slope of the linear curve (S) the isocratic parameter (φ 0 ) was calculated. Obtained retention factors were correlated with experimental log BB values for the group of examined compounds. High correlations were obtained between logarithm of biopartitioning micellar chromatography (BMC) retention factor and effective permeability (r(log k BMC /log BB): 0.77), while for RP-HPLC system the correlations were lower (r(log k wRP /log BB): 0.58; r(S/log BB): -0.50; r(φ 0 /P e ): 0.61). Based on the log k BMC retention data and calculated molecular parameters of the examined compounds, quantitative structure-permeability relationship (QSPR) models were developed using partial least squares, stepwise multiple linear regression, support vector machine and artificial neural network methodologies. A high degree of structural diversity of the analysed IRs/α-ARs ligands and CNS drugs provides wide applicability domain of the QSPR models for estimation of blood-brain barrier penetration of the related compounds.

Bioanalytical method for the estimation of co-administered esomeprazole, leflunomide and ibuprofen in human plasma and in pharmaceutical dosage forms using micellar liquid chromatography.

PubMed

Talaat, Wael

2017-05-01

The present study represents a connection between basic science and clinical applied science through providing a bioanalytical method for the analysis of certain co-administered drugs used for the treatment of rheumatoid arthritis. The studied drugs are esomeprazole, leflunomide and ibuprofen. The proposed bioanalytical method is a simple reversed phase high performance liquid chromatographic method using micellar mobile phase. The method is conducted using a Shim-pack VP-ODS (150 mm × 4.6 mm ID) stainless steel column at ambient temperature with ultraviolet detection at 285 nm. The micellar mobile phase consisted of 0.1 m sodium dodecyl sulfate, 10% n-propanol, 0.3% triethylamine in 0.02 m orthophosphoric acid (pH 3.5) and is pumped at a flow rate of 1.0 mL/min. The calibration curve was rectilinear over the concentration range of 0.1-5.0, 0.5-10.0 and 1.0-20.0 μg/mL for esomeprazole, leflunomide and ibuprofen respectively. The proposed method was successfully applied to the analysis of these drugs in dosage forms. The method is extended to the in-vitro, in-vivo determination of these drugs in spiked and real human plasma samples. Copyright © 2016 John Wiley & Sons, Ltd.

Branching, Superdiffusion and Stress Relaxation in Surfactant Micelles

NASA Astrophysics Data System (ADS)

Sureshkumar, R.; Dhakal, S.; Syracuse University Team

2016-11-01

We investigate the mechanism of branch formation and its effects on the dynamics and rheology of a model cationic micellar fluid using molecular dynamics (MD) simulations. Branched structures are formed upon increasing counter ion density. A sharp decrease in the solution viscosity with increasing salinity has long been attributed to the sliding motion of micellar branches along the main chain. Simulations not only provide firm evidence of branch sliding in real time, but also show enhanced diffusion of surfactants by virtue of such motion. Insights into the mechanism of stress relaxation associated with branch sliding will be discussed. Specifically, an externally imposed stress damps out more quickly in a branched system compared to that in an unbranched one. NSF Grants 1049489, 1049454.

A master dynamic flow diagram for the shear thickening transition in micellar solutions.

PubMed

Bautista, F; Tepale, N; Fernández, V V A; Landázuri, G; Hernández, E; Macías, E R; Soltero, J F A; Escalante, J I; Manero, O; Puig, J E

2016-01-07

The shear thickening behavior of dilute micellar solutions of hexadecyltrimethylammonium-type surfactants with different counterions (tosylate, 3- and 4-fluorobenzoate, vinylbenzoate and salicylate) and of n-alkyltetradecylammonium bromide (CnTAB), with n = 14, 16 and 18, is examined here. These solutions undergo a shear thickening transition due to the formation of shear-induced structures (SISs) in the shear range studied. Here we report a relationship between the shear thickening intensity and the differences in the hydrophobicity of counterions according to the Hofmeister-like anion series, which leads to a master flow diagram. This master flow diagram is produced by plotting a normalized shear thickening intensity (Iη - 1)/(Imax - 1) versus CD/CD,max, where Iη is the shear-thickening intensity, defined as the largest viscosity obtained in the shear-thickening transition (STT) at a given surfactant concentration CD divided by the Newtonian viscosity η0, and Imax is the largest intensity value obtained in the STT at a surfactant concentration CD,max. The master flow diagram is built using several cetyltrimethylammonium-type surfactants with different counterions, according to a Hofmeister-like series, and by n-alkyltetradecylammonium bromide surfactants with different alkyl chain lengths.

Determining the morphology of polystyrene-block-poly(2-vinylpyridine) micellar reactors for ZnO nanoparticle synthesis.

PubMed

El-Atwani, Osman; El-Atwani, Osman C; Aytun, Taner; Mutaf, Omer Faruk; Srot, Vesna; van Aken, Peter A; Ow-Yang, Cleva W

2010-05-18

We report the use of reverse PS-b-P2VP diblock copolymer micelles as true nanoscale-sized reactor vessels to synthesize ZnO nanoparticles. The reverse micelles were formed in toluene and then sequentially loaded with zinc acetate dihydrate and tetramethylammonium hydroxide reactants. Moreover, high spatial resolution Z-contrast imaging and EDX spectroscopy techniques were used to confirm the segregation of the Zn cation to the core of the loaded micelles. Determining the chemical distribution with high nanoscale spatial resolution is shown to complement the less direct characterization by AFM, DLS and FTIR, thus demonstrating broader implications for the characterization of hybrid nanocomposite systems.

Microviscoelasticity of adhesive hard sphere dispersions: Tracer particle microrheology of aqueous Pluronic L64 solutions

NASA Astrophysics Data System (ADS)

Kloxin, Christopher J.; van Zanten, John H.

2009-10-01

DWS-based tracer particle microrheology is demonstrated to be a useful way to study the dynamics of aqueous Pluronic L64 solutions, which is viewed as a model adhesive hard sphere (AHS) system. The short-time dynamics of aqueous Pluronic L64 solutions indicate a purely hydrodynamic high frequency microviscosity as predicted by Batchelor for colloidal dispersions. The evolution of the micellar dynamics reveals a zero shear microviscosity in good agreement with steady shear viscosity measurements. As the temperature is increased, the dynamics become dominated by an apparent attractive intermicellar potential observed in microscopic creep measurements. While Pluronic L64 solutions have been reported to form a percolated micellar network, DWS-based microviscoelasticity measurements do not detect the previously observed G'˜G″˜ωΔ scaling expected for a static percolated network at low frequencies. This most likely owes to the fact that tracer particle microrheology is dominated by local Pluronic L64 micelle dynamics in the near sphere region and not the bulk mechanical properties as measured by traditional rheometry. The sensitivity of tracer particle microrheological measurements to the true dynamic nature of the percolated network in weak physical gels highlights the distinct differences between these micro- and macrorheology measurement techniques. Such discrepancies should be most evident in systems that are dominated by association processes such as those occurring in AHS solutions or polymer solutions approaching a phase boundary. Despite this, the AHS potential is qualitatively consistent with the results found here.

Microviscoelasticity of adhesive hard sphere dispersions: tracer particle microrheology of aqueous Pluronic L64 solutions.

PubMed

Kloxin, Christopher J; van Zanten, John H

2009-10-07

DWS-based tracer particle microrheology is demonstrated to be a useful way to study the dynamics of aqueous Pluronic L64 solutions, which is viewed as a model adhesive hard sphere (AHS) system. The short-time dynamics of aqueous Pluronic L64 solutions indicate a purely hydrodynamic high frequency microviscosity as predicted by Batchelor for colloidal dispersions. The evolution of the micellar dynamics reveals a zero shear microviscosity in good agreement with steady shear viscosity measurements. As the temperature is increased, the dynamics become dominated by an apparent attractive intermicellar potential observed in microscopic creep measurements. While Pluronic L64 solutions have been reported to form a percolated micellar network, DWS-based microviscoelasticity measurements do not detect the previously observed G(') approximately G(") approximately omega(Delta) scaling expected for a static percolated network at low frequencies. This most likely owes to the fact that tracer particle microrheology is dominated by local Pluronic L64 micelle dynamics in the near sphere region and not the bulk mechanical properties as measured by traditional rheometry. The sensitivity of tracer particle microrheological measurements to the true dynamic nature of the percolated network in weak physical gels highlights the distinct differences between these micro- and macrorheology measurement techniques. Such discrepancies should be most evident in systems that are dominated by association processes such as those occurring in AHS solutions or polymer solutions approaching a phase boundary. Despite this, the AHS potential is qualitatively consistent with the results found here.

Formulation and evaluation of lecithin organogel for topical delivery of fluconazole.

PubMed

Jadhav, Kisan R; Kadam, Vilasrao J; Pisal, Sambhaji S

2009-04-01

The purpose of the present study was to develop and investigate the suitability of microemulsion based lecithin organogel formulations for topical delivery of fluconazole in order to bypass its gastrointestinal adverse effects. The ternary phase diagrams were developed and various organogel formulations were prepared using pharmaceutically acceptable surfactant (lecithin) and ethyl oleate (EO). Solubility of fluconazole in EO and EO-lecithin reverse micellar system was determined. The transdermal permeability of fluconazole from different concentrations of lecithin organogels containing EO as oil phase was analyzed using Keshary-Chien diffusion cell through excised rat skin. Solubility of fluconazole in EO-lecithin reverse micellar system was almost 3 folds higher than that in EO. Gelation and immobilization of oil require critical solubility-insolubility balance of gelator. The occurrence of gel phase was lecithin concentration dependent and was observed in 10-60% w/v of system. Organogel containing 300 mM of lecithin showed the higher drug release and better relative consistency. Hence, it was selected for antifungal activity. The increase in antifungal activity of fluconazole in lecithin organogel may be because of the surfactant action of the lecithin and EO that may help in the diffusion of drug. The histopathological data showed that EO-lecithin organogels were safe enough for the topical purpose. Hence, the present lecithin based organogel appears beneficial for topical delivery of fluconazole in terms of easy preparation, safety, stability and low cost.

Search of non-ionic surfactants suitable for micellar liquid chromatography.

PubMed

Peris-García, Ester; Rodríguez-Martínez, Jorge; Baeza-Baeza, Juan J; García-Alvarez-Coque, María Celia; Ruiz-Angel, María José

2018-06-19

Most reports in reversed-phase liquid chromatography (RPLC) with micellar mobile phases make use of the anionic sodium dodecyl sulfate. This surfactant masks efficiently the silanol groups that are the origin of the poor efficiencies and tailing peaks observed for basic compounds in conventional RPLC. However, it has the handicap of yielding excessive retention, which forces the addition of an organic solvent to reduce the retention times to practical values. Other surfactants, such as the non-ionic polyoxyethylene(23)lauryl ether (Brij-35), are rarely used. Brij-35 allows the separation of a large range of analytes in adequate retention times, without the need of adding an organic solvent to the mobile phase. However, this non-ionic surfactant shows irreversible adsorption on chromatographic columns and peak shape is poorer. Therefore, the search of non-ionic surfactants with similar properties to Brij-35, but showing reversible adsorption and better peak shape, can be of great interest. In this work, the adequacy of several non-ionic surfactants as modifiers in RPLC has been explored, being polyoxyethylene(10)tridecyl ether particularly attractive. The separation of different types of compounds was checked: sulfonamides (acidic), β-adrenoceptor antagonists and tricyclic antidepressants (basic with diverse polarity), and flavonoids (with and without hydroxyl groups on the aromatic rings). The chromatographic behaviors were examined in terms of retention and peak shape. The results were compared with those obtained with Brij-35.

Determination of solute descriptors by chromatographic methods.

PubMed

Poole, Colin F; Atapattu, Sanka N; Poole, Salwa K; Bell, Andrea K

2009-10-12

The solvation parameter model is now well established as a useful tool for obtaining quantitative structure-property relationships for chemical, biomedical and environmental processes. The model correlates a free-energy related property of a system to six free-energy derived descriptors describing molecular properties. These molecular descriptors are defined as L (gas-liquid partition coefficient on hexadecane at 298K), V (McGowan's characteristic volume), E (excess molar refraction), S (dipolarity/polarizability), A (hydrogen-bond acidity), and B (hydrogen-bond basicity). McGowan's characteristic volume is trivially calculated from structure and the excess molar refraction can be calculated for liquids from their refractive index and easily estimated for solids. The remaining four descriptors are derived by experiment using (largely) two-phase partitioning, chromatography, and solubility measurements. In this article, the use of gas chromatography, reversed-phase liquid chromatography, micellar electrokinetic chromatography, and two-phase partitioning for determining solute descriptors is described. A large database of experimental retention factors and partition coefficients is constructed after first applying selection tools to remove unreliable experimental values and an optimized collection of varied compounds with descriptor values suitable for calibrating chromatographic systems is presented. These optimized descriptors are demonstrated to be robust and more suitable than other groups of descriptors characterizing the separation properties of chromatographic systems.

Topical delivery of aceclofenac from lecithin organogels: preformulation study.

PubMed

Shaikh, I M; Jadhav, K R; Gide, P S; Kadam, V J; Pisal, S S

2006-10-01

The purpose of this research is to evaluate the suitability of lecithin organogels containing aceclofenac for topical application. The present article focuses on the preformulation part of the whole research work. Thin layer chromatography was carried out to determine lecithin's purity. The excipients for formulating lecithin organogel were screened. Lecithin organogels are thermo reversible in nature and hence gelation temperature study was carried out to determine the temperature where Sol-Gel and Gel-Sol transformation takes place. Partition coefficient of the drug was estimated. Drug solubility in plain oil and organogel containing reverse micelles was estimated. Effect of water added on the properties of lecithin organogels such as X-ray diffraction pattern, conductivity and viscosity were determined. Microscopy of the gel sample has been carried out at different magnifications. The pseudo ternary phase diagram has been constructed to determine the organogel existence region. The permeation study of aceclofenac from different concentrations of lecithin organogels [200 mM, 300 mM and 400 mM] has been determined using cellulose acetate membrane (0.45 micro) and excised rat skin. Lecithin organogel in ethyl oleate has desired stability and consistency. A single spot on the TLC plate confirms the purity of soy lecithin to be used in organogel formation. Aceclofenac solubility was found to be more in lecithin/oil reverse micellar system as compared to its solubility in oil. The X-ray diffraction pattern confirms the incorporation of water in micellar gel network. The physical properties of organogels are affected by water incorporated and concentration of gelator. The permeation of aceclofenac through artificial membrane and excised rat skin demonstrated the same trend and were in the following order 200 mM>300 mM>400 mM. The results showed that organogel exhibits useful pharmaceutical properties.

Simultaneous determination of gaseous and particulate carbonyls in air by coupling micellar electrokinetic capillary chromatography with molecular imprinting solid-phase extraction.

PubMed

Sun, Hui; Lai, Jia-Ping; Fung, Ying Sing

2014-09-05

A novel method coupling molecular imprinting solid-phase extraction (MISPE) and micellar electrokinetic capillary chromatography (MEKC) was developed to enable the hourly determination of low level of ambient carbonyls, and study their partition between gaseous phase and particulate phase. With 2,4-dinitroaniline (DNAN) as dummy imprinting template, the unreacted 2,4-Dinitrophenylhydrazine (DNPH) in sampling solution could be removed effectively using MISPE, and an average recovery of 97±5.3% (n=5) for the carbonyl-DNPH derivatives was achieved. Owing to the high enrichment due to sample clean-up, and the improvement of MEKC separation efficiency, many low abundant carbonyls could be detected by hourly in the field study. Copyright © 2014 Elsevier B.V. All rights reserved.

Amphiphilic Polysaccharide Block Copolymers for pH-Responsive Micellar Nanoparticles.

PubMed

Breitenbach, Benjamin B; Schmid, Ira; Wich, Peter R

2017-09-11

A full polysaccharide amphiphilic block copolymer was prepared from end group-functionalized dextrans using copper-mediated azide-alkyne click chemistry. Sufficient modification of the reducing end in both blocks was achieved by microwave-enhanced reductive amination in a borate-buffer/methanol solvent system. The combination of a hydrophilic dextran block with a hydrophobic acetalated dextran block results in an amphiphilic structure that turns water-soluble upon acid treatment. The material has a low critical micelle concentration and self-assembles in water to spherical micellar nanoparticles. The formed nanoparticles have a narrow size distribution below 70 nm in diameter and disassemble in slightly acidic conditions. The amphiphilic polysaccharide system shows low toxicity and can stabilize the hydrophobic model drug curcumin in aqueous solutions over extended time periods.

Self-organization of polymerizable bolaamphiphiles bearing diacetylene mesogenic group.

PubMed

Yin, Shouchun; Song, Bo; Liu, Guanqing; Wang, Zhiqiang; Zhang, Xi

2007-05-22

We report herein the synthesis of a series of polymerizable bolaamphiphiles containing a diacetylene group and mesogenic unit and their self-organization behaviors in bulk and at interface. The polymerizable bolaamphiphiles are noted as DPDA-n, where n refers to the spacer length of alkyl chain. DPDA-10 with suitable spacer length can self-organize into stable cylindrical micellar nanostructures, and these nanostructures have preferred orientation regionally when adsorbed at the mica/water interface. It is confirmed that the micellar nanostructure of DPDA-10 can be polymerized both in the bulk solution and in the film by UV irradiation. The emission property of DPDA-10 after UV irradiation has been significantly enhanced in comparison to that before polymerization, which may be due to the extension of the conjugated system arising from the transformation of the diacetylene group into polydiacetylene upon polymerization. In addition, the self-organization of DPDA-n is dependent on the spacer length. DPDA-7 with a short spacer length forms an irregular flat sheet structure with many defects; DPDA-15 with a long spacer length forms rodlike micellar structures. Thus, this work may provide a new approach for designing and fabricating organic functional nanostructured materials.

Flocculation of deformable emulsion droplets. 2: Interaction energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petsev, D.N.; Denkov, N.D.; Kralchevsky, P.A.

1995-12-01

The effect of different factors (drop radius, interfacial tension, Hamaker constant, electrolyte, micellar concentrations, etc.) on the interaction energy of emulsion droplets is studied theoretically. It is demonstrated that the deformation of the colliding droplets considerably affects the interaction energy. The contributions of the electrostatic, van der Waals, depletion, steric, and oscillatory surface forces, as well as for the surface stretching and bending energies, are estimated and discussed. The calculations show that the droplets interact as nondeformed spheres when the attractive interactions are weak. At stronger attractions an equilibrium plane parallel film is formed between the droplets, corresponding to minimummore » interaction energy of the system. For droplets in concentrated micellar surfactant solutions the oscillatory surface forces become operative and one can observe several minima of the energy surface,each corresponding to a metastable state with a different number of micellar layers inside the film formed between the droplets. The present theoretical analysis can find applications in predicting the behavior and stability of miniemulsions (containing micrometer and submicrometer droplets), as well as in interpretation of data obtained by light scattering, phase behavior, rheological and osmotic pressure measurements, etc.« less

[Cetyltrimethylammonium bromide for fluorescence enhancement of anhydrotetracycline hydrochloride and iso-tetracycline].

PubMed

Zha, Jian-peng; Lin, Ying; Yang, Xing-hui; Hou, Hai-ni; Wei, Tie-jun; Chen, Xing-li

2002-06-01

Fluorescence enhancement of anhydrotetracycline hydrochloride and iso-tetracycline has been described. The fluorescence intensities of anhydrotetracycline hydrochloride and iso-tetracycline with cetyltrimethylammonium bromide (CTMAB) enhanced by micellar solution have been examined. It is found that fluorescence enhancement of anhydrotetracycline hydrochloride and iso-tetracycline depends on the concentration of CTMAB and pH of the solution. It can be used to develop sensitive methods for the determination of tetracycline hydrochloride and its decomposition product.

Removal of copper ions from aqueous solutions by means of micellar-enhanced ultrafiltration

NASA Astrophysics Data System (ADS)

Kowalska, Izabela; Klimonda, Aleksandra

2017-11-01

The aim of the study was to assess the usefulness of micellar-enhanced ultrafiltration (MEUF) for removal of copper ions from water solutions in comparison with classic ultrafiltration process. The tests were conducted in a semi-pilot membrane installation with the use of ultrafiltration module KOCH/ROMICON® at a transmembrane pressure of 0.05 MPa. The effect of concentration of copper ions on ultrafiltration process efficiency was investigated. The second part of the tests concerned the removal of copper ions by MEUF under wide range of anionic surfactant concentration (0.25, 1, and 5 CMC (critical micelle concentration)). Concentration of copper ions in model solutions was equal to 5, 20, and 50 mg Cu/L. Furthermore, the effect of surfactant leakage to the permeate side during filtration was evaluated. Conducted experiments confirmed effectiveness of MEUF in copper ions removal. For the highest copper concentration in the feed (i.e. 50 mg/L), the average concentration of copper ions in the permeate ranged from 1.2-4.7 mg Cu/L depending on surfactant concentration. During filtration experiments, UF module exhibited stable transport properties for model solutions containing copper. For the highest concentration of metal, the decrease of permeate flux did not exceed 11% after 60 minutes of filtration. In the presence of the surfactant, a slight deterioration of transport properties was observed.

1H, 13C and 15N assignment of the C-terminal domain of GNA2132 from Neisseria meningitidis

PubMed Central

Esposito, Veronica; Musi, Valeria; Veggi, Daniele; Pizza, Mariagrazia

2010-01-01

GNA2132 (Genome-derived Neisseria Antigen 2132) is a surface-exposed lipoprotein discovered by reverse vaccinology and expressed by genetically diverse Neisseria meningitidis strains (Pizza et al. 2000). The protein induces bactericidal antibodies against most strains of Meningococccus and has been included in a multivalent recombinant vaccine against N. meningitidis serogroup B. Structure determination of GNA2132 is important for understanding the antigenic properties of the protein in view of increased efficiency vaccine development. We report practically complete 1H, 13C and 15N assignment of the detectable spectrum of a highly conserved C-terminal region of GNA2132 (residues 245–427) in micellar solution, a medium used to improve the spectral quality. The first 32 residues of our construct up to residue 277 were not visible in the spectrum, presumably because of line broadening due to solvent and/or conformational exchange. Secondary structure predictions based on chemical shift information indicate the presence of an all β-protein with eight β strands. PMID:20300890

Self-assembly of peptide-amphiphile nanofibers under physiological conditions

DOEpatents

Stupp, Samuel I [Chicago, IL; Hartgerink, Jeffrey D [Pearland, TX; Beniash, Elia [Auburndale, MA

2011-11-22

The present invention provides a method of promoting neuron growth and development by contacting cells with a peptide amphiphile molecule in an aqueous solution in the presence of a metal ion. According to the method, the peptide amphiphile forms a cylindrical micellar nanofiber composed of beta-sheets, which promote neuron growth and development.

Micellar electrokinetic chromatographic determination of triazine herbicides in water samples.

PubMed

Li, Zhi; Zhang, Shuaihua; Yin, Xiaofang; Wang, Chun; Wang, Zhi

2014-09-01

Dispersive liquid-liquid microextraction combined with online sweeping preconcentration in micellar electrokinetic chromatography was developed for the simultaneous determination of five triazine herbicides (atrazine, simazine, propazine, prometon and simetryn) in water samples. Several experimental parameters affecting the extraction efficiencies such as the type and volume of both the extraction and dispersive solvents, the addition of salt to sample solution, the extraction time and the pH of the sample solution were investigated. Under optimum conditions, the linearity of the method was good in the range from 0.33 to 20 ng mL(-1) for simazine, propazine, atrazine and simetryn, and from 0.17 to 20 ng mL(-1) for prometon, respectively. The sensitivity enrichment factors were in the range from 1750 to 2100, depending on the compound. The limit of detection (S/N = 3) ranged from 0.05 to 0.10 ng mL(-1). The developed method was successfully applied to the analysis of the five triazines in river, ground and well waters. © The Author [2013]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Synthesis of TiO{sub 2} nanoparticles by self-assembling reverse micelle cores of PS-b-PAA for functional textile applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akpolat, Leyla Budama; Çakır, Burçin Acar; Topel, Önder, E-mail: ondertopel@akdeniz.edu.tr

2015-04-15

Highlights: • TiO{sub 2} nanoparticles were synthesized within poly(styrene)-b-poly(acrylic acid) micelles. • The copolymer solution including nano TiO{sub 2} was coated onto textile fabrics. • UV-protective factor of nano TiO{sub 2} coated fabrics was estimated as 50+. • Nano TiO{sub 2} coated fabrics was found to exhibit a high photocatalytic activity. - Abstract: Titanium dioxide (i.e., titanium(IV) oxide, TiO{sub 2}) nanoparticles have been fabricated using a copolymer templating technique in micellar solution of poly(styrene)-block-poly(acrylic acid), PS(10912)-b-PAA(4842) synthesized by atom transfer radical polymerization (ATRP). The size and morphology of the synthesized TiO{sub 2} nanoparticles have been characterized via TEM and XRDmore » measurements. The average size of TiO{sub 2} nanoparticles was determined as 13 ± 3 and 13 ± 4 nm for titanium:copolymer ratios of 20:1 and 33:1, respectively. The copolymer solution including nano TiO{sub 2} particles has been coated onto textile fabrics to enhance their UV-blocking and self-cleaning properties. It has been determined that nano TiO{sub 2} coated textile fabrics have very good UV-blocking properties with 50+ of the ultraviolet protecting factor (UPF) and high photocatalytic efficiency with 69.2% of the photodegradation of methylene blue.« less

Origin of shear thickening in semidilute wormlike micellar solutions and evidence of elastic turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marín-Santibáñez, Benjamín M.; Pérez-González, José, E-mail: jpg@esfm.ipn.mx; Rodríguez-González, Francisco

2014-11-01

The origin of shear thickening in an equimolar semidilute wormlike micellar solution of cetylpyridinium chloride and sodium salicylate was investigated in this work by using Couette rheometry, flow visualization, and capillary Rheo-particle image velocimetry. The use of the combined methods allowed the discovery of gradient shear banding flow occurring from a critical shear stress and consisting of two main bands, one isotropic (transparent) of high viscosity and one structured (turbid) of low viscosity. Mechanical rheometry indicated macroscopic shear thinning behavior in the shear banding regime. However, local velocimetry showed that the turbid band increased its viscosity along with the shearmore » stress, even though barely reached the value of the viscosity of the isotropic phase. This shear band is the precursor of shear induced structures that subsequently give rise to the average increase in viscosity or apparent shear thickening of the solution. Further increase in the shear stress promoted the growing of the turbid band across the flow region and led to destabilization of the shear banding flow independently of the type of rheometer used, as well as to vorticity banding in Couette flow. At last, vorticity banding disappeared and the flow developed elastic turbulence with chaotic dynamics.« less

Small-angle neutron scattering study of the structure of mixed micellar solutions based on heptaethylene glycol monotetradecyl ether and cesium dodecyl sulfate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajewska, A., E-mail: aldonar@jinr.ru; Medrzycka, K.; Hallmann, E.

2016-01-15

The micellization in mixed aqueous systems based on a nonionic surfactant, heptaethylene glycol monotetradecyl ether (C{sub 14}E{sub 7}), and an anionic surfactant, cesium dodecyl sulfate, has been investigated by small-angle neutron scattering. Preliminary data on the behavior of the C{sub 14}E{sub 7} aqueous solutions (with three concentrations, 0.17, 0.5, and 1%) mixed with a small amount of anionic surfactant, cesium dodecyl sulfate, are reported.

Preparation and Properties of Hybrid Nanostructures of Zinc Tetraphenylporphyrinate and an Amphiphilic Copolymer of N-Vinylpyrrolidone in a Neutral Aqueous Buffer Solution

NASA Astrophysics Data System (ADS)

Kurmaz, S. V.; Gak, V. Yu.; Kurmaz, V. A.; Konev, D. V.

2018-02-01

Water-soluble forms of a hydrophobic dye, zinc tetraphenylporphyrinate, are obtained via its solubilization by polymer particles of the micellar type formed by a copolymer of N-vinylpyrrolidone with triethylene glycol dimethacrylate. Hydrodynamic radii R h and the size distribution of such particles in neutral aqueous buffer solutions are determined via dynamic light scattering. The electrochemical activity of the encapsulated dye is found, and its photochemical properties (absorption and fluorescence) are studied.

Effects of ethanol addition on micellar solubilization and plume migration during surfactant enhanced recovery of tetrachloroethene.

PubMed

Taylor, Tammy P; Rathfelder, Klaus M; Pennell, Kurt D; Abriola, Linda M

2004-03-01

Alcohol addition has been suggested for use in combination with surfactant flushing to enhance solubilization kinetics and permit density control of dense non-aqueous phase liquid (DNAPL)-laden surfactant plumes. This study examined the effects of adding ethanol (EtOH) to a 4% Tween 80 (polyoxyethylene (20) sorbitan monooleate) solution used to flush tetrachloroethene (PCE)-contaminated porous media. The influence of EtOH concentration, subsurface layering and scale on flushing solution delivery and PCE recovery was investigated through a combination of experimental and mathematical modeling studies. Results of batch experiments demonstrated that the addition of 2.5%, 5% and 10% (wt.) EtOH incrementally increased the PCE solubilization capacity and viscosity of the surfactant solution, while reducing solution density from 1.002 to 0.986 g/cm3. Effluent concentration data obtained from one-dimensional (1-D) column experiments were used to characterize rate-limited micellar solubilization of residual PCE, which was strongly dependent upon flow velocity and weakly dependent upon EtOH concentration. Two-dimensional (2-D) box studies illustrated that minor differences (0.008 g/cm3) between flushing and resident solution density can strongly influence surfactant front propagation. A two-dimensional multiphase simulator, MISER, was used to model the influence of EtOH composition on the aqueous flow field and PCE mass recovery. The ability of the numerical simulator to predict effluent concentrations and front propagation was demonstrated for both 1-D columns and 2-D boxes flushed with EtOH-amended Tween 80 solutions. Results of this study quantify the potential influence of alcohol addition on surfactant solution properties and solubilization capacity, and demonstrate the importance of considering small density variations in remedial design.

Conductivity, A Simple Method to Probe Micellar Solutions

NASA Astrophysics Data System (ADS)

Bachofer, Steven J.

1996-09-01

A conductivity experiment on the tetradecyltrimethylammonium X-benzoate surfactants and the corresponding sodium X-benzoate salts demonstrates how this physical property can be applied to the study of the complex equilibria of ionic micellar aggregates. The surfactant CMC and fractional ionization constant (alpha) values are determined from the conductivity measurements. A student class studies the surfactants, in which a number of substituted benzoate counterions are utilized, and can be introduced to Quantitative Structure-Activity Relationships (QSAR) to explain the resulting CMC values. High quality data can be recorded with ease. The data from a student class illustrate that CMC values are sensitive to the hydrophobicity of the X-benzoate anion. However, hydrophobicity is not the only important parameter to be considered. The student class can propose other important factors with some additional reading of the colloidal literature.

Absorption, fluorescence, and acid-base equilibria of rhodamines in micellar media of sodium dodecyl sulfate

NASA Astrophysics Data System (ADS)

Obukhova, Elena N.; Mchedlov-Petrossyan, Nikolay O.; Vodolazkaya, Natalya A.; Patsenker, Leonid D.; Doroshenko, Andrey O.; Marynin, Andriy I.; Krasovitskii, Boris M.

2017-01-01

Rhodamine dyes are widely used as molecular probes in different fields of science. The aim of this paper was to ascertain to what extent the structural peculiarities of the compounds influence their absorption, emission, and acid-base properties under unified conditions. The acid-base dissociation (HR+ ⇄ R + H+) of a series of rhodamine dyes was studied in sodium n-dodecylsulfate micellar solutions. In this media, the form R exists as a zwitterion R±. The indices of apparent ionization constants of fifteen rhodamine cations HR+ with different substituents in the xanthene moiety vary within the range of pKaapp = 5.04 to 5.53. The distinct dependence of emission of rhodamines bound to micelles on pH of bulk water opens the possibility of using them as fluorescent interfacial acid-base indicators.

Shape-selective synthesis of non-micellar cobalt oxide (CoO) nanomaterials by microwave irradiations

NASA Astrophysics Data System (ADS)

Kundu, Subrata; Jayachandran, M.

2013-04-01

Shape-selective formation of CoO nanoparticles has been developed using a simple one-step in situ non-micellar microwave (MW) heating method. CoO NPs were synthesized by mixing aqueous CoCl2·6H2O solution with poly (vinyl) alcohol (PVA) in the presence of sodium hydroxide (NaOH). The reaction mixture was irradiated using MW for a total time of 2 min. This process exclusively generated different shapes like nanosphere, nanosheet, and nanodendrite structures just by tuning the Co(II) ion to PVA molar ratios and controlling other reaction parameters. The proposed synthesis method is efficient, straightforward, reproducible, and robust. Other than in catalysis, these cobalt oxide nanomaterials can be used for making pigments, battery materials, for developing solid state sensors, and also as an anisotropy source for magnetic recording.

"Cut-off" effect of antioxidants and/or probes of variable lipophilicity in microheterogeneous media.

PubMed

Aliaga, Carolina; López de Arbina, Amaia; Rezende, Marcos Caroli

2016-09-01

The activities of two hydrophilic (ascorbic acid and Trolox) and two hydrophobic (α-tocopherol and BHT) antioxidants were measured by reaction with a series of 4-alkanoyloxyTEMPO radical probes 1 in buffered (pH 7), aqueous, micellar solutions of reduced Triton-X 100. In all cases, a cut-off effect was observed, in line with previous observations of the same effect for the partitioning of probe series 1 in this medium. These results support an interpretation of the cut-off effect in food emulsions, based on the "amphiphobic" nature of either the antioxidants or probes: competition between two molecular moieties, for the micellar hydrophobic core, tends to expose a reacting fragment differently to a more hydrophilic microenvironment, as the probe or antioxidant hydrophobicity increases. Copyright © 2016 Elsevier Ltd. All rights reserved.

Robust analysis of the hydrophobic basic analytes loratadine and desloratadine in pharmaceutical preparations and biological fluids by sweeping-cyclodextrin-modified micellar electrokinetic chromatography.

PubMed

El-Awady, Mohamed; Belal, Fathalla; Pyell, Ute

2013-09-27

The analysis of hydrophobic basic analytes by micellar electrokinetic chromatography (MEKC) is usually challenging because of the tendency of these analytes to be adsorbed onto the inner capillary wall in addition to the difficulty to separate these compounds as they exhibit extremely high retention factors. A robust and reliable method for the simultaneous determination of loratadine (LOR) and its major metabolite desloratadine (DSL) is developed based on cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) with acidic sample matrix and basic background electrolyte (BGE). The influence of the sample matrix on the reachable focusing efficiency is studied. It is shown that the application of a low pH sample solution mitigates problems associated with the low solubility of the hydrophobic basic analytes in aqueous solution while having advantages with regard to on-line focusing. Moreover, the use of a basic BGE reduces the adsorption of these analytes in the separation compartment. The separation of the studied analytes is achieved in less than 7min using a BGE consisting of 10mmolL(-1) disodium tetraborate buffer, pH 9.30 containing 40mmolL(-1) SDS and 20mmolL(-1) hydroxypropyl-β-CD while the sample solution is composed of 10mmolL(-1) phosphoric acid, pH 2.15. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in tablets without interference of tablet additives as well as the analysis of spiked human urine without any sample pretreatment. Furthermore, DSL can be detected as an impurity in LOR bulk powder at the stated pharmacopeial limit (0.1%, w/w). The selectivity of the developed method allows the analysis of LOR and DSL in combination with the co-formulated drug pseudoephedrine. It is shown that in CD-MEKC with basic BGE, solute-wall interactions are effectively suppressed allowing the development of efficient and precise methods for the determination of hydrophobic basic analytes, whereas the use of a low pH sample solution has a positive impact on the attainable sweeping efficiency without compromising peak shape and resolution. Copyright © 2013 Elsevier B.V. All rights reserved.

Potential Therapeutic Applications of Mucuna pruriens Peptide Fractions Purified by High-Performance Liquid Chromatography as Angiotensin-Converting Enzyme Inhibitors, Antioxidants, Antithrombotic and Hypocholesterolemic Agents.

PubMed

Herrera-Chalé, Francisco; Ruiz-Ruiz, Jorge Carlos; Betancur-Ancona, David; Segura-Campos, Maira Rubi

2016-02-01

A Mucuna pruriens protein concentrate was hydrolyzed with a digestive (pepsin-pancreatin) enzymatic system. The soluble portion of the hydrolysate was fractionated by ultrafiltration and the ultrafiltered peptide fraction (PF) with lower molecular weight was purified by reversed-phase high-performance liquid chromatography. The PF obtained were evaluated by testing the biological activity in vitro. Fractions showed that the ability to inhibit the angiotensin-converting enzyme had IC50 values that ranged from 2.7 to 6.2 μg/mL. Trolox equivalent antioxidant capacity values ranged from 132.20 to 507.43 mM/mg. The inhibition of human platelet aggregation ranged from 1.59% to 11.11%, and the inhibition of cholesterol micellar solubility ranged from 0.24% to 0.47%. Hydrophobicity, size, and amino acid sequence could be factors in determining the biological activity of peptides contained in fractions. This is the first report that M. pruriens peptides act as antihypertensives, antioxidants, and inhibitors for human platelet aggregation and cholesterol micellar solubility in vitro.

Intestinal absorption of retinol and retinyl palmitate in the rat. Effects of tetrahydrolipstatin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez, E.; Borgstroem, B.

1990-09-01

The aim of the present study was to characterize the intestinal absorption of retinol and retinyl palmitate in thoracic duct and bile duct fistulated rats and to investigate the effect of a simultaneously administered lipase inhibitor, tetrahydrolipstatin (THL). Absorption was determined as lymphatic recovery over a 24-hr period, including an initial 12-hr continuous intraduodenal infusion of either (11,12-3H)retinol or (11,12-3H)retinyl palmitate given in emulsified glyceryl trioleate or in mixed micellar solution of monoolein and oleic acid. From micellar dispersion, labeled retinol and retinyl palmitate were recovered in the lymph to 50-60% and both to the same extent. Administered in emulsifiedmore » form, labeled retinol from fed retinyl palmitate was recovered to 47%, but retinol from fed retinol to only 18%. THL (10(-4) M) in the infusate had no significant effect on the recovery of 14C-labeled oleic acid. The recovery of label from emulsified glyceryl tri(1-14C)oleate was significantly decreased at this concentration of THL (76.5% vs 19.6% recovery). When administered in emulsified form, retinol absorption was not significantly affected by THL at 10(-4) M, while retinyl palmitate absorption was very significantly decreased (5.0% compared to 47.8%). In the presence of THL, retinol absorption from retinyl palmitate in micellar solution was decreased (from 58% to 17%). Most of the retinol in the lymph extracts (72.2 to 91.3) was present as retinyl ester, regardless of the chemical and physical form of administration. Furthermore, THL did not induce any change in this pattern.« less

Influence of chain length and double bond on the aqueous behavior of choline carboxylate soaps.

PubMed

Rengstl, Doris; Diat, Olivier; Klein, Regina; Kunz, Werner

2013-02-26

In preceding studies, we demonstrated that choline carboxylates ChC(m) with alkyl chain lengths of m = 12 - 18 are highly water-soluble (for m = 12, soluble up to 93 wt % soap and 0 °C). In addition, choline soaps are featured by an extraordinary lyotropic phase behavior. With decreasing water concentration, the following phases were found: micellar phase (L(1)), discontinuous cubic phase (I(1)' and I(1)"), hexagonal phase (H(1)), bicontinuous cubic phase (V(1)), and lamellar phase (L(α)). The present work is also focused on the lyotropic phase behavior of choline soaps but with shorter alkyl chains or different alkyl chain properties. We have investigated the aqueous phase behavior of choline soaps with C(8) and C(10) chain-lengths (choline octanoate and choline decanoate) and with a C(18) chain-length with a cis-double bond (choline oleate). We found that choline decanoate follows the lyotropic phase behavior of the longer-chain homologues mentioned above. Choline octanoate in water shows no discontinuous cubic phases, but an extended, isotropic micellar solution phase. In addition, choline octanoate is at the limit between a surfactant and a hydrotrope. The double bond in choline oleate leads also to a better solubility in water and a decrease of the solubilization temperature. It also influences the Gaussian curvature of the aggregates which results in a loss of discontinuous cubic phases in the binary phase diagram. The different lyotropic mesophases were identified by the penetration scan technique with polarizing light microscope and visual observations. To clarify the structural behavior small (SAXS) and wide (WAXS) angle X-ray scattering were performed. To further characterize the extended, isotropic micellar solution phase in the binary phase diagram of choline octanoate viscosity and conductivity measurements were also carried out.

The fabrication of highly ordered block copolymer micellar arrays: control of the separation distances of silicon oxide dots

NASA Astrophysics Data System (ADS)

Yoo, Hana; Park, Soojin

2010-06-01

We demonstrate the fabrication of highly ordered silicon oxide dotted arrays prepared from polydimethylsiloxane (PDMS) filled nanoporous block copolymer (BCP) films and the preparation of nanoporous, flexible Teflon or polyimide films. Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films were annealed in toluene vapor to enhance the lateral order of micellar arrays and were subsequently immersed in alcohol to produce nano-sized pores, which can be used as templates for filling a thin layer of PDMS. When a thin layer of PDMS was spin-coated onto nanoporous BCP films and thermally annealed at a certain temperature, the PDMS was drawn into the pores by capillary action. PDMS filled BCP templates were exposed to oxygen plasma environments in order to fabricate silicon oxide dotted arrays. By addition of PS homopolymer to PS-b-P2VP copolymer, the separation distances of micellar arrays were tuned. As-prepared silicon oxide dotted arrays were used as a hard master for fabricating nanoporous Teflon or polyimide films by spin-coating polymer precursor solutions onto silicon patterns and peeling off. This simple process enables us to fabricate highly ordered nanoporous BCP templates, silicon oxide dots, and flexible nanoporous polymer patterns with feature size of sub-20 nm over 5 cm × 5 cm.

The fabrication of highly ordered block copolymer micellar arrays: control of the separation distances of silicon oxide dots.

PubMed

Yoo, Hana; Park, Soojin

2010-06-18

We demonstrate the fabrication of highly ordered silicon oxide dotted arrays prepared from polydimethylsiloxane (PDMS) filled nanoporous block copolymer (BCP) films and the preparation of nanoporous, flexible Teflon or polyimide films. Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films were annealed in toluene vapor to enhance the lateral order of micellar arrays and were subsequently immersed in alcohol to produce nano-sized pores, which can be used as templates for filling a thin layer of PDMS. When a thin layer of PDMS was spin-coated onto nanoporous BCP films and thermally annealed at a certain temperature, the PDMS was drawn into the pores by capillary action. PDMS filled BCP templates were exposed to oxygen plasma environments in order to fabricate silicon oxide dotted arrays. By addition of PS homopolymer to PS-b-P2VP copolymer, the separation distances of micellar arrays were tuned. As-prepared silicon oxide dotted arrays were used as a hard master for fabricating nanoporous Teflon or polyimide films by spin-coating polymer precursor solutions onto silicon patterns and peeling off. This simple process enables us to fabricate highly ordered nanoporous BCP templates, silicon oxide dots, and flexible nanoporous polymer patterns with feature size of sub-20 nm over 5 cm x 5 cm.

Partitioning of nitroxides in dispersed systems investigated by ultrafiltration, EPR and NMR spectroscopy.

PubMed

Krudopp, Heimke; Sönnichsen, Frank D; Steffen-Heins, Anja

2015-08-15

The partitioning behavior of paramagnetic nitroxides in dispersed systems can be determined by deconvolution of electron paramagnetic resonance (EPR) spectra giving equivalent results with the validated methods of ultrafiltration techniques (UF) and pulsed-field gradient nuclear magnetic resonance spectroscopy (PFG-NMR). The partitioning behavior of nitroxides with increasing lipophilicity was investigated in anionic, cationic and nonionic micellar systems and 10 wt% o/w emulsions. Apart from EPR spectra deconvolution, the PFG-NMR was used in micellar solutions as a non-destructive approach, while UF based on separation of very small volume of the aqueous phase. As a function of their substituent and lipophilicity, the proportions of nitroxides that were solubilized in the micellar or emulsion interface increased with increasing nitroxide lipophilicity for all emulsifier used. Comparing the different approaches, EPR deconvolution and UF revealed comparable nitroxide proportions that were solubilized in the interfaces. Those proportions were higher than found with PFG-NMR. For PFG-NMR self-diffusion experiments the reduced nitroxides were used revealing a high dynamic of hydroxylamines and emulsifiers. Deconvolution of EPR spectra turned out to be the preferred method for measuring the partitioning behavior of paramagnetic molecules as it enables distinguishing between several populations at their individual solubilization sites. Copyright © 2015 Elsevier Inc. All rights reserved.

Insights into molecular architecture of terpenes using small angle neutron scattering

NASA Astrophysics Data System (ADS)

Rai, Durgesh K.; Annamraju, Aparna; Pingali, Sai Venkatesh; O'Neill, Hugh M.; Mewalal, Ritesh; Gunter, Lee E.; Tuskan, Gerald A.

Understanding macromolecular architectures is vital to engineering prospective terpene candidates for advanced biofuels. Eucalyptus plants store terpenes in specialized cavity-like structures in the leaves called oil glands, which comprises of volatile (VTs) and non-volatile (NVTs) terpenes. Using small-angle neutron scattering, we have investigated the structure and phase behavior of the supramolecular assembly formed by Geranyl beta-D-glucoside (GDG), a NVT and compare the results with that of beta-octyl glucoside (BOG). The formation of micellar structures was observed in the concentration range of 0.5-5 v/v% in water using small angle neutron scattering (SANS) where Schultz sphere model was used in quantifying structural parameters of micelles. SANS studies determine that GDG and BOG behave like amphiphiles forming micellar structures in aqueous solution. The micelles swell upon addition of alpha-Pinene (AP) indicating partition to the core region of the micelles. The general behavior of the micellar growth after partitioning of AP to form thermodynamically stable sizes varies with the NVT concentration. Our studies reveal that the presence of steric hindrance in the GDG via the unsaturated bonds could help stabilize VTs inside the oil glands. LDRD project LOIS ID 7428, SNS, CSMB, HFIR, ORNL, DOE Office of Science User Facilities.

Aggregation behavior and complex structure between triblock copolymer and anionic surfactants

NASA Astrophysics Data System (ADS)

Li, Yiming; Bao, Mutai; Wang, Zhining; Zhang, Haixia; Xu, Guiying

2011-01-01

The aggregation behavior and complex structure of ABA triblock copolymer EO 76PO 30EO 76 (F68) with sodium dodecyl sulfate (SDS) and sodium bis(2-ethylhexyl)sulfonate (AOT) in aqueous solution were investigated by surface tension, fluorescence techniques and dynamic light-scattering (DLS) measurements. It is revealed that in certain regions of binding, surfactant/F68 complexes are formed. Structural informations and size of complexes are evaluated. When F68 is present in its nonassociated state, F68/micellar SDS complexes are formed at SDS concentrations above its critical aggregation concentration (cac). The cac is well below the critical micellar concentration (cmc) of pure SDS, and a model suggesting how complexes are formed at the cac in the presence of F68 is described. Experimental results show that SDS interacts with F68 mainly through hydrophobic forces, polypropylene oxide (PPO) groups of F68 are solubilized into SDS micellar cores and poly(ethylene oxide) (PEO) groups interact with SDS micelles. This interaction mechanism results in a "pearl-necklace" complex structure. However, a different structure occurs for F68/AOT complex at lower F68 concentrations, as nonassociated F68 interacts with AOT mainly through ion-dipole interactions. Complexes with a "wrapping" structure at lower F68 concentrations are formed.

Micellar systems: Novel family for drug carriers

NASA Astrophysics Data System (ADS)

Rana, Meenakshi; Chowdhury, Papia

2016-05-01

Micellar systems have attracted a great deal of interest, especially in the field of biomedical sciences. The paper deals with the encapsulation behavior of Pyrrole-2-carboxyldehyde (PCL) an anti-cancer drug in different micellar systems. The inculsion capability of PCL is verified experimentally (UV-Vis, Photoluminescence and Raman spectroscopy) in polymer matrix. Two-micellar systems sodium dodecyl sulfate (SDS) and Polysorbate 80 (TWEEN 80) have been studied with a poorly water soluble PCL. The present work provides the effects of biocompatible organic PCL molecule entrap in micellar system in polymer phase due to its vast applicability in drug industry.

A Randomized Trial Investigating the Efficacy and Safety of Water Soluble Micellar Paclitaxel (Paccal Vet) for Treatment of Nonresectable Grade 2 or 3 Mast Cell Tumors in Dogs

PubMed Central

Vail, D.M.; von Euler, H.; Rusk, A.W.; Barber, L.; Clifford, C.; Elmslie, R.; Fulton, L.; Hirschberger, J.; Klein, M.; London, C.; Martano, M.; McNiel, E.A.; Morris, J.S.; Northrup, N.; Phillips, B.; Polton, G.; Post, G.; Rosenberg, M.; Ruslander, D.; Sahora, A.; Siegel, S.; Thamm, D.; Westberg, S.; Winter, J.; Khanna, C.

2013-01-01

Background Effective treatments for dogs with advanced stage mast cell tumors (MCT) remain a pressing need. A micellar formulation of paclitaxel (paclitaxel [micellar]) has shown promise in early-phase studies. Hypothesis/Objectives The objective was to demonstrate greater activity for paclitaxel (micellar) compared with lomustine. The null hypothesis was μp = μL (ie, proportion of responders for the paclitaxel [micellar] and lomustine groups, respectively). Animals Two hundred and fifty-two dogs with advanced stage nonresectable grade 2 or 3 MCT. Methods Prospective multicenter randomized double-blind positive-controlled clinical trial. The primary endpoint was confirmed overall response rate (CORR) at 14 weeks. A secondary endpoint, biologic observed response rate (BORR), also was calculated. Safety was assessed by the characterization and grading of adverse events (AE). Results Overall CORR (7% versus 1%; P = .048) and BORR (23% versus 10%; P = .012) were greater for paclitaxel (micellar) compared with lomustine. Paclitaxel (micellar)-treated dogs were 6.5 times more likely to have a confirmed response and 3.1 times more likely to experience a biologic observed response. The majority of AE with paclitaxel (micellar) were transient and clinically manageable. Twenty-seven dogs (33%) receiving lomustine were discontinued because of hepatopathy compared with 3 dogs (2%) receiving paclitaxel (micellar) (P < .0001; odds ratio 26.7). Conclusions and Clinical Importance Paclitaxel (micellar)’s activity and safety profile are superior to lomustine. The addition of an active and novel taxane to the veterinary armamentarium could fill a substantial need and, as its mechanism of action and AE profile do not overlap with currently available TKI, its availability could lead to effective combination protocols. PMID:22390318

The self-association of acebutolol: Conductometry and light scattering

NASA Astrophysics Data System (ADS)

Ruso, Juan M.; López-Fontán, José L.; Prieto, Gerardo; Sarmiento, Félix

2003-04-01

The association characteristics of an amphiphilic beta-blocker drug, acebutolol hydrochloride, in aqueous solution containing high concentrations of electrolyte and at different temperatures have been examined by static and dynamic light scattering and electrical conductivity. Time averaged light scattering measurements on aqueous solutions of acebutolol at 298.15 K in the presence of added electrolyte (0.4-1.0 mol kg-1 NaCl) have shown discontinuities which reflect the appearance of aggregates. The critical micelle concentration, aggregation numbers, effective micelle charges, and degree of micellar ionization were calculated. Dynamic light scattering has shown an increase in micellar size with increase in concentration of added electrolyte. Data have been interpreted using the DLVO theory to quantify the interaction between the drug aggregates and the colloidal stability. Critical micelle concentrations in water have been calculated from conductivity measurements over the temperature range 288.15-313.15 K. The variation in critical concentration with temperature passes through a minimum close to 294 K. Thermodynamic parameters of aggregate formation (ΔGm0,ΔHm0,ΔSm0) were obtained from a variation of the mass action model applicable to systems of low aggregation number.

Stimulus-Responsive Nanoparticles and Associated (Reversible) Polymorphism via Polymerization Induced Self-assembly (PISA).

PubMed

Pei, Yiwen; Lowe, Andrew B; Roth, Peter J

2017-01-01

Polymerization-induced self-assembly (PISA) is an extremely versatile method for the in situ preparation of soft-matter nanoparticles of defined size and morphologies at high concentrations, suitable for large-scale production. Recently, certain PISA-prepared nanoparticles have been shown to exhibit reversible polymorphism ("shape-shifting"), typically between micellar, worm-like, and vesicular phases (order-order transitions), in response to external stimuli including temperature, pH, electrolytes, and chemical modification. This review summarises the literature to date and describes molecular requirements for the design of stimulus-responsive nano-objects. Reversible pH-responsive behavior is rationalised in terms of increased solvation of reversibly ionized groups. Temperature-triggered order-order transitions, conversely, do not rely on inherently thermo-responsive polymers, but are explained based on interfacial LCST or UCST behavior that affects the volume fractions of the core and stabilizer blocks. Irreversible morphology transitions, on the other hand, can result from chemical post-modification of reactive PISA-made particles. Emerging applications and future research directions of this "smart" nanoparticle behavior are reviewed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dependence of the form factor of ganglioside micelles on a conformational change with temperature

NASA Astrophysics Data System (ADS)

Corti, Mario; Boretta, Marco; Cantù, Laura; Del Favero, Elena; Lesieur, Pierre

1996-09-01

The gangliosides GM2, GM1 and GD1b, biological amphiphiles with a double tail hydrophobic part and an oligosaccharide chain headgroup, form micelles in solution. Light scattering experiments have shown that ganglioside micelles which have gone through a temperature cycle have a smaller molecular mass and hydrodynamic radius than those which have been kept at room temperature. This fact has been interpreted with the hypothesis that, with temperature, the ganglioside molecules undergo a conformational change which affects their micellar properties appreciably. Careful small angle X-ray experiments, aimed to confirm the light scattering data and to evidence differences in the micellar internal structure are presented. Ganglioside micelles are quite inhomogeneous particles with respect to X-ray scattering, since there is a large contrast variation between the inner lipid part and the external hydrated sugar layer. Experimental form factors are fitted with a double-shell oblate-ellipsoid model.

One-step route to the fabrication of highly porous polyaniline nanofiber films by using PS-b-PVP diblock copolymers as templates.

PubMed

Li, Xue; Tian, Shengjun; Ping, Yang; Kim, Dong Ha; Knoll, Wolfgang

2005-10-11

We report a new method to control both the nucleation and growth of highly porous polyaniline (PANI) nanofiber films using porous poly(styrene-block-2-vinylpyridine) diblock copolymer (PS-b-P2VP) films as templates. A micellar thin film composed of P2VP spheres within a PS matrix is prepared by spin coating a PS-b-P2VP micellar solution onto substrates. The P2VP domains are swollen in a selective solvent of acetic acid, which results in the formation of pores in the block copolymer film. PANI is then deposited onto the substrates modified with such a porous film using electrochemical methods. During the deposition, the nucleation and growth of PANI occur only at the pores of the block copolymer film. After the continued growth of PANI by the electrochemical deposition, a porous PANI nanofiber film is obtained.

Controlling the interparticle spacing of Au-salt loaded micelles and Au nanoparticles on flat surfaces.

PubMed

Bansmann, J; Kielbassa, S; Hoster, H; Weigl, F; Boyen, H G; Wiedwald, U; Ziemann, P; Behm, R J

2007-09-25

The self-organization of diblock copolymers into micellar structures in an appropriate solvent allows the deposition of well ordered arrays of pure metal and alloy nanoparticles on flat surfaces with narrow distributions in particle size and interparticle spacing. Here we investigated the influence of the materials (substrate and polymer) and deposition parameters (temperature and emersion velocity) on the deposition of metal salt loaded micelles by dip-coating from solution and on the order and inter-particle spacing of the micellar deposits and thus of the metal nanoparticle arrays resulting after plasma removal of the polymer shell. For identical substrate and polymer, variation of the process parameters temperature and emersion velocity enables the controlled modification of the interparticle distance within a certain length regime. Moreover, also the degree of hexagonal order of the final array depends sensitively on these parameters.

Photosensitized electron transfer processes in SiO2 colloids and sodium lauryl sulfate micellar systems: Correlation of quantum yields with interfacial surface potentials

PubMed Central

Laane, Colja; Willner, Itamar; Otvos, John W.; Calvin, Melvin

1981-01-01

The effectiveness of negatively charged colloidal SiO2 particles in controlling photosensitized electron transfer reactions has been studied and compared with that of the negatively charged sodium lauryl sulfate (NaLauSO4) micellar system. In particular, the photosensitized reduction of the zwitterionic electron acceptor propylviologen sulfonate (PVS0) with tris(2,2′-bipyridinium)ruthenium(II) [Ru(bipy)32+] as the sensitizer and triethanolamine as the electron donor is found to have a quantum yield of 0.033 for formation of the radical anion (PVS[unk]) in the SiO2 colloid compared with 0.005 in the homogeneous system and 0.0086 in a NaLauSO4 micellar solution. The higher quantum yields obtained with the SiO2 colloidal system are attributed to substantial stabilization against back reaction of the intermediate photoproducts—i.e., Ru(bipy)33+ and PVS[unk]—by electrostatic repulsion of the reduced electron acceptor from the negatively charged particle surface. The binding properties of the SiO2 particles and NaLauSO4 micelles were investigated by flow dialysis. The results show that the sensitizer binds to both interfaces and that the SiO2 interface is characterized by a much higher surface potential than the micellar interface (≈-170 mV vs. -85 mV). The effect of ionic strength on the surface potential was estimated from the Gouy-Chapman theory, and the measured quantum yields of photosensitized electron transfer were correlated with surface potential at different ionic strengths. This correlation shows that the quantum yield is not affected by surface potentials smaller than ≈-40 mV. At larger potentials, the quantum yield increases rapidly. The quantum yield obtained in the micellar system at different strengths fits nicely on the correlation curve for the colloid SiO2 system. These results indicate that the surface potential is the dominant factor in the quantum yield improvement for PVS0 reduction. PMID:16593095

Role of surface elasticity in the drainage of soap films

NASA Astrophysics Data System (ADS)

Sonin, A. A.; Bonfillon, A.; Langevin, D.

1993-10-01

We present measurements of the thinning velocity of circular horizontal soap films made from dilute surfactant solutions (around the critical micellar concentration). We have solved numerically the hydrodynamic equations for the drainage process. After data fitting, we deduce the values of the elasticities of the surfactant monolayer that stabilizes the soap film. These elasticity values have been compared to elasticities obtained independently from the study of waves at the surface of the solution. The comparison reveals the importance of surface convection in the drainage process and demonstrates the important role of surface elasticity.

Comparison between micellar liquid chromatography and capillary zone electrophoresis for the determination of hydrophobic basic drugs in pharmaceutical preparations.

PubMed

Torres-Cartas, S; Martín-Biosca, Y; Sagrado, S; Villanueva-Camañas, R M; Medina-Hernández, M J

2007-01-01

The determination of highly hydrophobic basic compounds by means of conventional reversed-phase liquid chromatographic methods has several drawbacks. Owing to the characteristics of micellar liquid chromatography (MLC) and capillary electrophoresis (CE), these techniques could be advantageous alternatives to reversed-phase chromatographic methods for the determination of these kinds of compounds. The objective of this study was to develop and compare MLC and CE methods for the determination of antipsychotic basic drugs (amitryptiline, haloperidol, perphenazine and thioridazine) in pharmaceutical preparations. The chromatographic determination of the analytes was performed on a Kromasil C(18) analytical column; the mobile phase was 0.04 m cetyltrimethylammonium bromide (CTAB), at pH 3, containing 5% 1-butanol, at a flow rate of 1 mL/min. The CE separation was performed in a fused-silica capillary with a 50 mm tris-(hydroxymethyl)-aminomethane buffer, pH 7, at an applied voltage of 20 kV, using barbital as internal stardard. The proposed methods are suitable for a reliable quantitation of these compounds in the commercial tablets and drops in terms of accuracy and precision and require a very simple pre-treatment of the samples. By comparing the performance characteristics and experimental details of the MLC and CE methods we conclude that CE seems to be slightly better than MLC in the determination of highly hydrophobic compounds in pharmaceuticals in terms of resolution and economy, taking into account that the limits of detection are not a handicap in pharmaceutical samples. Copyright 2006 John Wiley & Sons, Ltd.

Effect of ripening, heat processing, and fat type on the micellarization of pigments from jalapeño peppers.

PubMed

Victoria-Campos, Claudia I; Ornelas-Paz, José de Jesús; Yahia, Elhadi M; Jiménez-Castro, Jorge A; Cervantes-Paz, Braulio; Ibarra-Junquera, Vrani; Pérez-Martínez, Jaime David; Zamudio-Flores, Paul B; Escalante-Minakata, Pilar

2013-10-16

Raw and heat-processed (boiled and grilled) jalapeño peppers at three intermediate ripening stages (brown, 50% red, and 75% red) were digested in vitro without fat and in the presence of soybean oil (SO) or beef tallow (BT), and the micellarization of their lipid soluble pigments (LSP) was measured. The micelles from digestions with brown, 50% red, and 75% red peppers contained up to 27, 35, and 29 different LSP, respectively. Boiling and grilling decreased the micellarization of LSP from brown peppers, whereas the opposite was observed with 75% red peppers. Heat processing did not clearly affect the micellarization of LSP from 50% red fruits. The impact of fat on LSP micellarization was ripening-dependent, but the micellarization of the less polar carotenoids was always increased by SO or BT. This positive effect of fat was higher with SO than with BT.

Counting ions and other nucleophiles at surfaces by chemical trapping.

PubMed

Cuccovia, Iolanda Midea; da Silva Lima, Filipe; Chaimovich, Hernan

2017-10-01

The interfaces of membranes and other aggregates are determined by the polarity, electrical charge, molecular volume, degrees of motional freedom and packing density of the head groups of the amphiphiles. These properties also determine the type of bound ion (ion selectivity) and its local density, i.e. concentration defined by choosing an appropriate volume element at the aggregate interface. Bulk and local ion concentrations can differ by orders of magnitude. The relationships between ion (or other compound) concentrations in the bulk solvent and in the interface are complex but, in some cases, well established. As the local ion concentration, rather than that in the bulk, controls a variety of properties of membranes, micelles, vesicles and other objects of theoretical and applied interests, measurement of local (interfacial, bound) ion concentrations is of relevance for understanding and characterizing such aggregates. Many experimental methods for estimating ion distributions between the bulk solution and the interface provide indirect estimates because they are based on concentration-dependent properties, rather than concentration measurements. Dediazoniation, i.e. the loss of N 2 , of a substituted diazophenyl derivative provides a tool for determining the number of nucleophiles (including neutral or negatively charged ions) surrounding the diazophenyl derivative prior to the dediazoniation event. This reaction, defined as chemical trapping, and the appropriate reference points obtained in bulk solution allow direct measurements of local concentrations of a variety of nucleophiles at the surface of membranes and other aggregates. Here we review our contributions of our research group to the use, and understanding, of this method and applications of chemical trapping to the description of local concentrations of ions and other nucleophiles in micelles, reverse micelles, vesicles and solvent mixtures. Among other results, we have shown that interfacial water determines micellar shape, zwitterionic vesicle-forming amphiphiles display ion selectivity and urea does not accumulate at micellar interfaces. We have also shown that reaction products can be predicted from the composition of the initial state, even in non-ideal solvent mixtures, supporting the usefulness of chemical trapping as a method to determine local concentrations. In addition, we have analysed the mechanism of dediazoniation, both on theoretical and experimental basis, and concluded that the formation of a free phenyl cation is not a necessary part of the reaction pathway.

pH-responsive supramolecular self-assembly of well-defined zwitterionic ABC miktoarm star terpolymers.

PubMed

Liu, Hao; Li, Changhua; Liu, Hewen; Liu, Shiyong

2009-04-21

We report the first example of the synthesis and pH-responsive supramolecular self-assembly of double hydrophilic ABC miktoarm star terpolymers. Well-defined ABC miktoarm star terpolymers consisting of poly(ethylene glycol), poly(tert-butyl methacrylate), and poly(2-(diethylamino)ethyl methacrylate) arms [PEG(-b-PtBMA)-b-PDEA] were synthesized via the combination of consecutive click reactions and atom transfer radical polymerization (ATRP), starting from a trifunctional core molecule, 1-azido-3-chloro-2-propanol (ACP). The click reaction of monoalkynyl-terminated PEG with an excess of ACP afforded difunctional PEG bearing a chlorine and a secondary hydroxyl moiety at the chain end, PEG113(-Cl)-OH (1). After azidation with NaN3, PEG-based macroinitiator PEG113(-N3)-Br (3) was prepared by the esterification of PEG113(-N3)-OH (2) with 2-bromoisobutyryl bromide and then employed in the ATRP of tert-butyl methacrylate (tBMA). The obtained PEG(-N3)-b-PtBMA copolymers (4) possessed an azido moiety at the diblock junction point. The preparation of PEG(-b-PtBMA)-b-PDEA miktoarm star terpolymers was then achieved via the click reaction of 4 with an excess of monoalkynyl-terminated PDEA. The obtained miktoarm star terpolymers were successfully converted into PEG(-b-PMAA)-b-PDEA, where PMAA is poly(methacrylic acid). In aqueous solution, PEG(-b-PMAA)-b-PDEA zwitterionic ABC miktoarm star terpolymers can self-assemble into three types of micellar aggregates by simply adjusting solution pH at room temperature. Above pH 8, PDEA-core micelles stabilized by PEG/ionized PMAA hybrid coronas were formed due to the insolubility of PDEA block. In the range of pH 5-7, micelles possessing polyion complex cores formed as a result of charge compensation between partially ionized PMAA and partially protonated PDEA sequences. At pH<4, hydrogen bonding interactions between fully protonated PMAA and PEG led to the formation of another type of micellar aggregates possessing hydrogen-bonded complex cores stabilized by protonated PDEA coronas. The fully reversible pH-responsive formation of three types of aggregates were characterized by 1H NMR, dynamic and static laser light scattering (LLS), and transmission electron microscopy (TEM).

Formation and Characterization of Anisotropic Block Copolymer Gels

NASA Astrophysics Data System (ADS)

Liaw, Chya Yan; Joester, Derk; Burghardt, Wesley; Shull, Kenneth

2012-02-01

Cylindrical micelles formed from block copolymer solutions closely mimic biological fibers that are presumed to guide mineral formation during biosynthesis of hard tissues like bone. The goal of our work is to use acrylic block copolymers as oriented templates for studying mineral formation reactions in model systems where the structure of the underlying template is well characterized and reproducible. Self-consistent mean field theory is first applied to investigate the thermodynamically stable micellar morphologies as a function of temperature and block copolymer composition. Small-angle x-ray scattering, optical birefringence and shear rheometry are used to study the morphology development during thermal processing. Initial experiments are based on a thermally-reversible alcohol-soluble system that can be converted to an aqueous gel by hydrolysis of a poly(t-butyl methacrylate) block to a poly(methacrylic acid) block. Aligned cylindrical domains are formed in the alcohol-based system when shear is applied in an appropriate temperature regime, which is below the critical micelle temperature but above the temperature at which the relaxation time of the gels becomes too large. Processing strategies for producing the desired cylindrical morphologies are being developed that account for both thermodynamic and kinetic effects.

Study of complex molecular systems by probe vibrational spectroscopy method

NASA Astrophysics Data System (ADS)

Boldeskul, A. E.; Zatsepin, V. M.; Atakhodjaev, A. K.; Shermatov, A. N.; Ashburiev, R.

1984-03-01

Experimental study of benzonitril as a probe in aqueous solution of sodium lauril sulphate /SDS/ by Raman spectroscopy technique showed integral moments of √ /C X N/ line to be extremely sensitive to the structural transitions in micellar systems. The central part of the experimental contour was used to determine integral moments with the help of line shape approximant received by Mori method

Paclitaxel-loaded polymeric microparticles: Quantitative relationships between in vitro drug release rate and in vivo pharmacodynamics

PubMed Central

Tsai, Max; Lu, Ze; Wientjes, M. Guillaume; Au, Jessie L.-S.

2013-01-01

Intraperitoneal therapy (IP) has demonstrated survival advantages in patients with peritoneal cancers, but has not become a widely practiced standard-of-care in part due to local toxicity and sub-optimal drug delivery. Paclitaxel-loaded, polymeric microparticles were developed to overcome these limitations. The present study evaluated the effects of microparticle properties on paclitaxel release (extent and rate) and in vivo pharmacodynamics. In vitro paclitaxel release from microparticles with varying physical characteristics (i.e., particle size, copolymer viscosity and composition) was evaluated. A method was developed to simulate the dosing rate and cumulative dose released in the peritoneal cavity based on the in vitro release data. The relationship between the simulated drug delivery and treatment outcomes of seven microparticle compositions was studied in mice bearing IP human pancreatic tumors, and compared to that of the intravenous Cremophor micellar paclitaxel solution used off-label in previous IP studies. Paclitaxel release from polymeric microparticles in vitro was multi-phasic; release was greater and more rapid from microparticles with lower polymer viscosities and smaller diameters (e.g., viscosity of 0.17 vs. 0.67 dl/g and diameter of 5–6 vs. 50–60 μm). The simulated drug release in the peritoneal cavity linearly correlated with treatment efficacy in mice (r2>0.8, p<0.001). The smaller microparticles, which distribute more evenly in the peritoneal cavity compared to the large microparticles, showed greater dose efficiency. For single treatment, the microparticles demonstrated up to 2-times longer survival extension and 4-times higher dose efficiency, relative to the paclitaxel/Cremophor micellar solution. Upon repeated dosing, the paclitaxel/Cremophor micellar solution showed cumulative toxicity whereas the microparticle that yielded 2-times longer survival did not display cumulative toxicity. The efficacy of IP therapy depended on both temporal and spatial factors that were determined by the characteristics of the drug delivery system. A combination of fast- and slow-releasing microparticles with 5–6 μm diameter provided favorable spatial distribution and optimal drug release for IP therapy. PMID:24056144

Flow of wormlike micellar solutions around confined microfluidic cylinders.

PubMed

Zhao, Ya; Shen, Amy Q; Haward, Simon J

2016-10-26

Wormlike micellar (WLM) solutions are frequently used in enhanced oil and gas recovery applications in porous rock beds where complex microscopic geometries result in mixed flow kinematics with strong shear and extensional components. Experiments with WLM solutions through model microfluidic porous media have revealed a variety of complex flow phenomena, including the formation of stable gel-like structures known as a Flow-Induced Structured Phase (FISP), which undoubtedly play an important role in applications of WLM fluids, but are still poorly understood. A first step in understanding flows of WLM fluids through porous media can be made by examining the flow around a single micro-scale cylinder aligned on the flow axis. Here we study flow behavior of an aqueous WLM solution consisting of cationic surfactant cetyltrimethylammonium bromide (CTAB) and a stable hydrotropic salt 3-hydroxy naphthalene-2-carboxylate (SHNC) in microfluidic devices with three different cylinder blockage ratios, β. We observe a rich sequence of flow instabilities depending on β as the Weissenberg number (Wi) is increased to large values while the Reynolds number (Re) remains low. Instabilities upstream of the cylinder are associated with high stresses in fluid that accelerates into the narrow gap between the cylinder and the channel wall; vortex growth upstream is reminiscent of that seen in microfluidic contraction geometries. Instability downstream of the cylinder is associated with stresses generated at the trailing stagnation point and the resulting flow modification in the wake, coupled with the onset of time-dependent flow upstream and the asymmetric division of flow around the cylinder.

The effect of ultrasound on casein micelle integrity.

PubMed

Chandrapala, J; Martin, G J O; Zisu, B; Kentish, S E; Ashokkumar, M

2012-12-01

Samples of fresh skim milk, reconstituted micellar casein, and casein powder were sonicated at 20 kHz to investigate the effect of ultrasonication. For fresh skim milk, the average size of the remaining fat globules was reduced by approximately 10 nm after 60 min of sonication; however, the size of the casein micelles was determined to be unchanged. A small increase in soluble whey protein and a corresponding decrease in viscosity also occurred within the first few minutes of sonication, which could be attributed to the breakup of casein-whey protein aggregates. No measurable changes in free casein content could be detected in ultracentrifuged skim milk samples sonicated for up to 60 min. A small, temporary decrease in pH resulted from sonication; however, no measurable change in soluble calcium concentration was observed. Therefore, casein micelles in fresh skim milk were stable during the exposure to ultrasonication. Similar results were obtained for reconstituted micellar casein, whereas larger viscosity changes were observed as whey protein content was increased. Controlled application of ultrasound can be usefully applied to reverse process-induced protein aggregation without affecting the native state of casein micelles. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Applications of micellar enzymology to clean coal technology. [Laccase from Polyporus versicolor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walsh, C.T.

1990-07-24

This project is designed to develop methods for pre-combustion coal remediation by implementing recent advances in enzyme biochemistry. The novel approach of this study is incorporation of hydrophilic oxidative enzymes in reverse micelles in an organic solvent. Enzymes from commercial sources or microbial extracts are being investigated for their capacity to remove organic sulfur from coal by oxidation of the sulfur groups, splitting of C-S bonds and loss of sulfur as sulfuric acid. Dibenzothiophen (DBT) and ethylphenylsulfide (EPS) are serving as models of organic sulfur-containing components of coal in initial studies.

Block copolymer micelles as switchable templates for nanofabrication.

PubMed

Krishnamoorthy, Sivashankar; Pugin, Raphaël; Brugger, Juergen; Heinzelmann, Harry; Hoogerwerf, Arno C; Hinderling, Christian

2006-04-11

Block copolymer inverse micelles from polystyrene-block-poly-2-vinylpyridine (PS-b-P2VP) deposited as monolayer films onto surfaces show responsive behavior and are reversibly switchable between two states of different topography and surface chemistry. The as-coated films are in the form of arrays of nanoscale bumps, which can be transformed into arrays of nanoscale holes by switching through exposure to methanol. The use of these micellar films to act as switchable etch masks for the structuring of the underlying material to form either pillars or holes depending on the switching state is demonstrated.

Pyrene As a New Detector for Determining the Composition of Silver Nanoparticle Dispersions in Aqueous Solutions

NASA Astrophysics Data System (ADS)

Romanovskaya, G. I.; Kazakova, S. Yu.; Koroleva, M. V.; Zuev, B. K.

2018-03-01

It is proposed that the fluorescence of monomeric molecules of pyrene in solid matrices or in concentrated micellar solutions be used as a detector for determining the compositional homogeneity of silver nanoparticle (NP) dispersions in aqueous solutions synthesized in different ways. It is found that the morphology of silver NPs affects the change in the fluorescence intensity of monomeric molecules of pyrene in a certain (violet or blue) region of the pyrene optical spectrum. The observed phenomenon is attributed to the resonance of electronic transitions in the monomeric molecules of pyrene in regions with plasmon oscillations in silver nanoparticles. A new way of obtaining fluorescent silver NPs is found.

Spontaneously self-assembled micelles from poly(ethylene glycol)-b-poly(epsilon-caprolactone-co-trimethylene carbonate) for drug solubilization.

PubMed

Latere, Dwan'Isa J P; Rouxhet, L; Brewster, M E; Préat, V; Ariën, A

2008-03-01

Di-block copolymers composed of polyethylene glycol (PEG) and a second block of (co)polyesters of epsilon-caprolactone (CL) and/or trimethylene carbonate (TMC) were synthesized and characterized. Tin octoate was used as catalyst and polymerization were completed over a period of 24 h with high conversion (> 95%). Self-assembling properties in water were evaluated. All di-block copolymers behave similarly except when PCL served as the second block. Stable crew-cut micelles of about 20 nm were obtained by direct dissolution of the liquid di-block copolymers in water at room temperature. When PCL was present as the second block, no solubilization occurred. Drug encapsulation of poorly water-soluble drugs belonging to biopharmaceutics classification system (BCS) class II (ketoprofen and furosemide) was evaluated. Experimental solubility for these two drugs shows a significant enhancement such that a maximum value of 23.4 mg/ml was obtained for ketoprofen in a 10% w/v micellar solution as compared to 0.14 mg in water. In the case of furosemide, the solubility increased from 0.04 mg/ml in water to about 3.2 mg/ml in a 10% w/v micellar solution. Enzymatic degradation of diblock copolymers was also studied in the presence of Pseudomonas lipase in a phosphate buffer solution (pH 7.4). Results indicated rapid degradation of copolymers containing relatively higher amounts of CL compared to TMC suggesting the potential in vivo degradation.

Phospholipid Nonwoven Electrospun Membranes

NASA Astrophysics Data System (ADS)

McKee, Matthew G.; Layman, John M.; Cashion, Matthew P.; Long, Timothy E.

2006-01-01

Nonwoven fibrous membranes were formed from electrospinning lecithin solutions in a single processing step. As the concentration of lecithin increased, the micellar morphology evolved from spherical to cylindrical, and at higher concentrations the cylindrical micelles overlapped and entangled in a fashion similar to polymers in semi-dilute or concentrated solutions. At concentrations above the onset of entanglements of the wormlike micelles, electrospun fibers were fabricated with diameters on the order of 1 to 5 micrometers. The electrospun phospholipid fibers offer the potential for direct fabrication of biologically based, high-surface-area membranes without the use of multiple synthetic steps, complicated electrospinning designs, or postprocessing surface treatments.

Impact of thermooxidation of phytosteryl and phytostanyl fatty acid esters on cholesterol micellarization in vitro.

PubMed

Scholz, Birgit; Weiherer, Renate; Engel, Karl-Heinz

2017-09-01

The effects of thermooxidation of a phytosteryl/-stanyl and a phytostanyl fatty acid ester mixture on cholesterol micellarization were investigated using an in vitro digestion model simulating enzymatic hydrolysis by cholesterol esterase and subsequent competition of the liberated phytosterols/-stanols with cholesterol for incorporation into mixed micelles. As a first step, relationships between different doses of the ester mixtures and the resulting micellarized cholesterol were established. Subsequent subjection of the thermooxidized ester mixtures to the in vitro digestion model resulted in three principal observations: (i) thermal treatment of the ester mixtures led to substantial decreases of the intact esters, (ii) in vitro digestion of cholesterol in the presence of the thermooxidized ester mixtures resulted in significant increases of cholesterol micellarization, and (iii) the extents of the observed effects on cholesterol micellarization were strongly associated to the remaining contents of intact esters. The loss of efficacy to inhibit cholesterol micellarization due to thermally induced losses of intact esters corresponded to a loss of efficacy that would have been induced by an actual removal of these amounts of esters prior to the in vitro digestion. The obtained results suggest that in particular oxidative modifications of the fatty acid moieties might be responsible for the observed increases of cholesterol micellarization. Copyright © 2017 Elsevier Inc. All rights reserved.

Biological activity and photostability of biflorin micellar nanostructures.

PubMed

Santana, Edson R B; Ferreira-Neto, João P; Yara, Ricardo; Sena, Kêsia X F R; Fontes, Adriana; Lima, Cláudia S A

2015-05-13

Capraria biflora L. is a shrub from the Scrophulariaceae family which produces in its roots a compound named biflorin, an o-naphthoquinone that shows activity against Gram-positive bacteria and fungi and also presents antitumor and antimetastatic activities. However, biflorin is hydrophobic and photosensitive. These properties make its application difficult. In this work we prepared biflorin micellar nanostructures looking for a more effective vehiculation and better preservation of the biological activity. Biflorin was obtained, purified and characterized by UV-Vis, infrared (IR) and 1H- and 13C-NMR. Micellar nanostructures of biflorin were then assembled with Tween 80®, Tween 20® and saline (0.9%) and characterized by UV-Vis spectroscopy and dynamic light scattering (DLS). The results showed that the micellar nanostructures were stable and presented an average size of 8.3 nm. Biflorin micellar nanostructures' photodegradation was evaluated in comparison with biflorin in ethanol. Results showed that the biflorin in micellar nanostructures was better protected from light than biflorin dissolved in ethanol, and also indicated that biflorin in micelles were efficient against Gram-positive bacteria and yeast species. In conclusion, the results showed that the micellar nanostructures could ensure the maintenance of the biological activity of biflorin, conferring photoprotection. Moreover, biflorin vehiculation in aqueous media was improved, favoring its applicability in biological systems.

Monte Carlo and mean-field studies of phase evolution in concentrated surfactant solutions

NASA Astrophysics Data System (ADS)

Bohbot, Yardena; Ben-Shaul, Avinoam; Granek, Rony; Gelbart, William M.

1995-11-01

A two-dimensional lattice model, originally introduced by Granek et al. [J. Chem. Phys. 101, 4331 (1994)], is used to demonstrate the intricate coupling between the intramicellar interactions that determine the optimal aggregation geometry of surfactant molecules in dilute solution, and the intermicellar interactions that govern the phase behavior at higher concentrations. Three very different scenarios of self-assembly and phase evolution are analyzed in detail, based on Monte Carlo studies and theoretical interpretations involving mean-field, Landau-Ginzburg, Bethe-Peierls, and virial expansion schemes. The basic particles in the model are ``unit micelles'' which, due to spontaneous self-assembly or because of excluded area interactions, can fuse to form larger aggregates. These aggregates are envisaged as flat micelles composed of a bilayerlike body surrounded by a curved semitoroidal rim. The system's Hamiltonian involves one- through four-body potentials between the unit micelles, which account for their tendency to form aggregates of different shapes, e.g., elongated vs disklike micelles. Equivalently, the configurational energy of the system is a sum of micellar self-energies involving the packing free energies of the constituent molecules in the bilayer body and in rim segments of different local curvature. The rim energy is a sum of a line tension term and a 1D curvature energy which depends on the rim spontaneous curvature and bending rigidity. Different combinations of these molecular parameters imply different optimal packing geometries and hence different self-assembly and phase behaviors. The emphasis in this paper is on systems of ``curvature loving'' amphiphiles which, in our model, are characterized by negative line tension. The three systems studied are: (i) A dilute solution of stable disklike micelles which, upon increasing the concentration, undergoes a first-order phase transition to a continuous bilayer with isolated hole defects. An intermediate modulated ``checkerboard'' phase appears under certain conditions at low temperatures. (ii) A system of unit micelles which in dilute solution tend to associate into linear micelles. These micelles are rodlike at low temperatures, becoming increasingly more flexible as the temperature increases. Upon increasing the concentration the micelles grow and undergo (in 2D) a continuous transition into nematic and ``stripe'' phases of long rods. At still higher concentrations the micellar stripes fuse into continuous sheets with line defects. (iii) A system in which, already in dilute solution, the micelles favor the formation of branched aggregates, analogous to the branched cylindrical micelles recently observed in certain surfactant solutions. As the concentration increases the micelles associate into networks (``gels'') composed of a mesh of linear micelles linked by ``T-like'' intermicellar junctions. The network may span the entire system or phase separate and coexist with a dilute micellar phase, depending on the details of the molecular packing parameters.

Product yield-detected ESR on magnetic field-dependent photoreduction of quinones in SDS micellar solution

NASA Astrophysics Data System (ADS)

Okazaki, M.; Sakata, S.; Konaka, R.; Shiga, T.

1987-06-01

Transient free radicals in the magnetic field-dependent photoreduction of quinones (menadione or anthraquinone) in a sodium dodecyl sulfate (SDS) micellar solution, were converted to stable nitroxide radicals by the ``spin trapping'' technique with or without the microwave irradiation. Upon irradiating the microwave at 160 mW, the product yield (``spin adduct'' of the alkyl radical generated from SDS molecule) decreased by up to 14% at certain magnetic fields in a resonant manner. Although only one component of the postulated radical pair was converted to the spin adduct, the decrease in the yield as a function of external magnetic field revealed the ESR spectra of both component radicals of the radical pair, i.e., the semiquinone radical and the alkyl radical from SDS. This experiment not only gives the direct evidence for the radical pair model, but also suggests the possibility for this method to be applied in controlling the chemical reactions by the microwave. A simple calculation was made to simulate the observed ``product yield-detected ESR.'' Agreements were achieved semiquantitatively between the observed reductions in the spin adduct yields and those calculated. The estimated exchange interaction between the component radicals in the radical pair of the present systems was lower than 0.3 mT.

Protochlorophyll complexes with similar steady-state fluorescence characteristics can differ in fluorescence lifetimes. A model study in Triton X-100.

PubMed

Myśliwa-Kurdziel, Beata; Solymosi, Katalin; Kruk, Jerzy; Böddi, Béla; Strzałka, Kazimierz

2007-03-01

The steady-state and time-resolved fluorescence characteristics of protochlorophyll (Pchl) dissolved in neat Triton X-100 and in Triton X-100 micelles were investigated, and the fluorescence lifetimes of different Pchl spectral forms were studied. Varying the concentration of Pchl or diluting the micellar solutions either with a buffer or with a micellar solution, 631-634, 645-655, 680-692 and above 700 nm emitting Pchl complexes were prepared, the ratios of which varied from one another. The fluorescence decay of the 631-634 nm emitting (monomeric) form had a mono-exponential character with a 5.4-ns fluorescence lifetime. The long-wavelength Pchl complexes (aggregates) had two fluorescence lifetime values within a range of 1.4-3.9 ns and 0.15-0.84 ns, which showed high variability in different environments. Depending on the conditions, either mono- or double-exponential fluorescence decay was found for a fluorescence band at 680-685 nm. These data show that despite their very similar steady-state fluorescence properties, Pchl complexes can differ in fluorescence lifetimes, which may reflect different molecular structures, intrinsic geometries or different molecular interactions. This underlines the importance of complex spectroscopic analysis for a precise description of native and artificial chlorophyllous pigment forms.

Micellar Self-Assembly of Recombinant Resilin-/Elastin-Like Block Copolypeptides.

PubMed

Weitzhandler, Isaac; Dzuricky, Michael; Hoffmann, Ingo; Garcia Quiroz, Felipe; Gradzielski, Michael; Chilkoti, Ashutosh

2017-08-14

Reported here is the synthesis of perfectly sequence defined, monodisperse diblock copolypeptides of hydrophilic elastin-like and hydrophobic resilin-like polypeptide blocks and characterization of their self-assembly as a function of structural parameters by light scattering, cryo-TEM, and small-angle neutron scattering. A subset of these diblock copolypeptides exhibit lower critical solution temperature and upper critical solution temperature phase behavior and self-assemble into spherical or cylindrical micelles. Their morphologies are dictated by their chain length, degree of hydrophilicity, and hydrophilic weight fraction of the ELP block. We find that (1) independent of the length of the corona-forming ELP block there is a minimum threshold in the length of the RLP block below which self-assembly does not occur, but that once that threshold is crossed, (2) the RLP block length is a unique molecular parameter to independently tune self-assembly and (3) increasing the hydrophobicity of the corona-forming ELP drives a transition from spherical to cylindrical morphology. Unlike the self-assembly of purely ELP-based block copolymers, the self-assembly of RLP-ELPs can be understood by simple principles of polymer physics relating hydrophilic weight fraction and polymer-polymer and polymer-solvent interactions to micellar morphology, which is important as it provides a route for the de novo design of desired nanoscale morphologies from first principles.

A systematic coarse-graining strategy for semi-dilute copolymer solutions: from monomers to micelles.

PubMed

Capone, Barbara; Coluzza, Ivan; Hansen, Jean-Pierre

2011-05-18

A systematic coarse-graining procedure is proposed for the description and simulation of AB diblock copolymers in selective solvents. Each block is represented by a small number, n(A) or n(B), of effective segments or blobs, containing a large number of microscopic monomers. n(A) and n(B) are unequivocally determined by imposing that blobs do not, on average, overlap, even if complete copolymer coils interpenetrate (semi-dilute regime). Ultra-soft effective interactions between blobs are determined by a rigorous inversion procedure in the low concentration limit. The methodology is applied to an athermal copolymer model where A blocks are ideal (theta solvent), B blocks self-avoiding (good solvent), while A and B blocks are mutually avoiding. The model leads to aggregation into polydisperse spherical micelles beyond a critical micellar concentration determined by Monte Carlo simulations for several size ratios f of the two blocks. The simulations also provide accurate estimates of the osmotic pressure and of the free energy of the copolymer solutions over a wide range of concentrations. The mean micellar aggregation numbers are found to be significantly lower than those predicted by an earlier, minimal two-blob representation (Capone et al 2009 J. Phys. Chem. B 113 3629).

A constitutive rheological model for agglomerating blood derived from nonequilibrium thermodynamics

NASA Astrophysics Data System (ADS)

Tsimouri, Ioanna Ch.; Stephanou, Pavlos S.; Mavrantzas, Vlasis G.

2018-03-01

Red blood cells tend to aggregate in the presence of plasma proteins, forming structures known as rouleaux. Here, we derive a constitutive rheological model for human blood which accounts for the formation and dissociation of rouleaux using the generalized bracket formulation of nonequilibrium thermodynamics. Similar to the model derived by Owens and co-workers ["A non-homogeneous constitutive model for human blood. Part 1. Model derivation and steady flow," J. Fluid Mech. 617, 327-354 (2008)] through polymer network theory, each rouleau in our model is represented as a dumbbell; the corresponding structural variable is the conformation tensor of the dumbbell. The kinetics of rouleau formation and dissociation is treated as in the work of Germann et al. ["Nonequilibrium thermodynamic modeling of the structure and rheology of concentrated wormlike micellar solutions," J. Non-Newton. Fluid Mech. 196, 51-57 (2013)] by assuming a set of reversible reactions, each characterized by a forward and a reverse rate constant. The final set of evolution equations for the microstructure of each rouleau and the expression for the stress tensor turn out to be very similar to those of Owens and co-workers. However, by explicitly considering a mechanism for the formation and breakage of rouleaux, our model further provides expressions for the aggregation and disaggregation rates appearing in the final transport equations, which in the kinetic theory-based network model of Owens were absent and had to be specified separately. Despite this, the two models are found to provide similar descriptions of experimental data on the size distribution of rouleaux.

Colloidal chirality in wormlike micellar systems exclusively originated from achiral species: Role of secondary assembly and stimulus responsivity.

PubMed

Zhao, Wenrong; Hao, Jingcheng

2016-09-15

Colloidal chirality in wormlike micellar systems exclusively originated from achiral species and discussion of the role of secondary assembly of fiber-like aggregates in chirality generation were presented in this paper. Herein, formation of colloidal wormlike micelles for the first time incorporated chirality and redox-responsiveness into one design via noncovalent interaction. A dual-stimuli-responsive gel of wormlike micelles which were designed by employing a dual-responsive cationic surfactant (FTMA) and a strong gelator (AzoNa4) and regulated by redox reaction and host-guest inclusion is presented. Both the redox and host-guest interaction play an important role in regulating the viscosity and supramolecular chirality of gels of the wormlike micelles. The supramolecular chirality and viscosity of the wormlike micelle gels were switched reversibly by exerting chemical redox onto the ferrocenyl groups. For the amphiphile FTMA containing redox-active ferrocenyl group, reversible control of the oxidation state of ferrocenyl groups leads to the charge and hydrophobicity changes of FTMA, therefore change its self-assembly behavior. Of equal interest, β-CD successfully detached the wormlike micelles via the recognition-inclusion behavior with FTMA and invalidate the H-bond and hydrophobic interaction between FTMA and AzoH4. This designed system provides a new strategy to tune the supramolecular chirality of colloidal aggregates and explore the specific packing mode detail within the micelles or the secondary assembly of the inter-micelles. We anticipate this dual-responsive H-bond-directed chiral gel switch could propose a new strategy when researchers designing new, multi-responsive functional gel materials. Copyright © 2016 Elsevier Inc. All rights reserved.

Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling-micellar electrokinetic chromatography-mass spectrometry with reversal of electroosmotic flow.

PubMed

Ge, Liya; Yong, Jean Wan Hong; Tan, Swee Ngin; Hua, Lin; Ong, Eng Shi

2008-05-01

In this paper, we present the results of simultaneous screening of eight gibberellins (GAs) in coconut (Cocos nucifera L.) water by MEKC directly coupled to ESI-MS detection. During the development of MEKC-MS, partial filling (PF) was used to prevent the micelles from reaching the mass spectrometer as this is detrimental to the MS signal, and a cationic surfactant, cetyltrimethylammonium hydroxide, was added to the electrolyte to reverse the EOF. On the basis of the resolution of the neighboring peaks, different parameters (i.e., the pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF-MEKC separation of eight GA standards. Under optimum conditions, a baseline separation of GA standards, including GA1, GA3, GA5, GA6, GA7, GA9, GA12, and GA13, was accomplished within 25 min. Satisfactory results were obtained in terms of precision (RSD of migration time below 0.9%), sensitivity (LODs in the range of 0.8-1.9 microM) and linearity (R2 between 0.981 and 0.997). MS/MS with multiple reaction monitoring (MRM) detection was carried out to obtain sufficient selectivity. PF-MEKC-MS/MS allowed the direct identification and confirmation of the GAs presented in coconut water (CW) sample after SPE, while, the quantitative analysis of GAs was performed by PF-MEKC-MS approach. GA1 and GA3 were successfully detected and quantified in CW. It is anticipated that the current PF-MEKC-MS method can be applicable to analyze GAs in a wide range of biological samples.

Preparation and in vitro evaluation of folate-receptor-targeted SPION-polymer micelle hybrids for MRI contrast enhancement in cancer imaging

NASA Astrophysics Data System (ADS)

Mahajan, Shveta; Koul, Veena; Choudhary, Veena; Shishodia, Gauri; Bharti, Alok C.

2013-01-01

Polymer-SPION hybrids were investigated for receptor-mediated localization in tumour tissue. Superparamagnetic iron oxide nanoparticles (SPIONs) prepared by high-temperature decomposition of iron acetylacetonate were monodisperse (9.27 ± 3.37 nm), with high saturation magnetization of 76.8 emu g-1. Amphiphilic copolymers prepared from methyl methacrylate and PEG methacrylate by atom transfer radical polymerization were conjugated with folic acid (for folate-receptor specificity). The folate-conjugated polymer had a low critical micellar concentration (0.4 mg l-1), indicating stability of the micellar formulation. SPION-polymeric micelle clusters were prepared by desolvation of the SPION dispersion/polymer solution in water. Magnetic resonance imaging of the formulation revealed very good contrast enhancement, with transverse (T2) relaxivity of 260.4 mM-1 s-1. The biological evaluation of the SPION micelles included cellular viability assay (MTT) and uptake in HeLa cells. These studies demonstrated the potential use of these nanoplatforms for imaging and targeting.

Crystallization in Micellar Cores: confinement effects and dynamics

NASA Astrophysics Data System (ADS)

Lund, Reidar; Zinn, Thomas; Willner, Lutz; Department of Chemistry, University of Oslo Team; Forschungszentrum Jülich Collaboration

It is well known that liquids confined to small nanoscopic pores and droplets exhibit thermal behavior very different from bulk samples. Here we demonstrate that n-alkanes forming 2-3 nm small micellar cores are considerably affected by confinement in analogue with hard confined systems. We study micelles form by self-assembly of a series of well-defined n-Alkyl-PEO polymers in aqueous solutions. By using small-angle X-ray scattering (SAXS), densiometry and differential scanning calorimetry (DSC), we show that n-alkane exhibit a first-order phase transition i.e. melting. Correlating the structural and thermodynamic data, we find that a melting depression can be accurately described by the Gibbs-Thomson equation. ∖f1 The effect of core crystallinity on the molecular exchange kinetics is investigated using time-resolved small-angle neutron scattering (TR-SANS). We show that there are considerable entropic and enthalpic contributions from the chain packing that affect the kinetic stability of micelles. ∖pard

Modeling the Inhomogeneous Response of Steady and Transient Flows of Entangled Micellar Solutions

NASA Astrophysics Data System (ADS)

McKinley, Gareth

2008-03-01

Surfactant molecules can self-assemble in solution into long flexible structures known as wormlike micelles. These structures entangle, forming a viscoelastic network similar to those in entangled polymer melts and solutions. However, in contrast to `inert' polymeric networks, wormlike micelles continuously break and reform leading to an additional relaxation mechanism and the name `living polymers'. Observations in both classes of entangled fluids have shown that steady and transient shearing flows of these solutions exhibit spatial inhomogeneities such as `shear-bands' at sufficiently large applied strains. In the present work, we investigate the dynamical response of a class of two-species elastic network models which can capture, in a self-consistent manner, the creation and destruction of elastically-active network segments, as well as diffusive coupling between the microstructural conformations and the local state of stress in regions with large spatial gradients of local deformation. These models incorporate a discrete version of the micellar breakage and reforming dynamics originally proposed by Cates and capture, at least qualitatively, non-affine tube deformation and chain disentanglement. The `flow curves' of stress and apparent shear rate resulting from an assumption of homogeneous deformation is non-monotonic and linear stability analysis shows that the region of non-monotonic response is unstable. Calculation of the full inhomogeneous flow field results in localized shear bands that grow linearly in extent across the gap as the apparent shear rate increases. Time-dependent calculations in step strain, large amplitude oscillatory shear (LAOS) and in start up of steady shear flow show that the velocity profile in the gap and the total stress measured at the bounding surfaces are coupled and evolve in a complex non-monotonic manner as the shear bands develop and propagate.

Current trends in the use of vitamin E-based micellar nanocarriers for anticancer drug delivery.

PubMed

Muddineti, Omkara Swami; Ghosh, Balaram; Biswas, Swati

2017-06-01

Owing to the complexity of cancer pathogenesis, conventional chemotherapy can be an inadequate method of killing cancer cells effectively. Nanoparticle-based drug delivery systems have been widely exploited pre-clinically in recent years. Areas covered: Incorporation of vitamin-E in nanocarriers have the advantage of (1) improving the hydrophobicity of the drug delivery system, thereby improving the solubility of the loaded poorly soluble anticancer drugs, (2) enhancing the biocompatibility of the polymeric drug carriers, and (3) improving the anticancer potential of the chemotherapeutic agents by reversing the cellular drug resistance via simultaneous administration. In addition to being a powerful antioxidant, vitamin E demonstrated its anticancer potential by inducing apoptosis in various cancer cell lines. Various vitamin E analogs have proven their ability to cause marked inhibition of drug efflux transporters. Expert opinion: The review discusses the potential of incorporating vitamin E in the polymeric micelles which are designed to carry poorly water-soluble anticancer drugs. Current applications of various vitamin E-based polymeric micelles with emphasis on the use of α-tocopherol, D-α-tocopheryl succinate (α-TOS) and its conjugates such as D-α-tocopheryl polyethylene glycol-succinate (TPGS) in micellar system is delineated. Advantages of utilizing polymeric micelles for drug delivery and the challenges to treat cancer, including multiple drug resistance have been discussed.

Directly Observing Micelle Fusion and Growth in Solution by Liquid-Cell Transmission Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parent, Lucas R.; Bakalis, Evangelos; Ramírez-Hernández, Abelardo

Amphiphilic small molecules and polymers form commonplace nanoscale macromolecular compartments and bilayers, and as such are truly essential components in all cells and in many cellular processes. The nature of these architectures, including their formation, phase changes, and stimuli-response behaviors, is necessary for the most basic functions of life, and over the past half-century, these natural micellar structures have inspired a vast diversity of industrial products, from biomedicines to detergents, lubricants, and coatings. The importance of these materials and their ubiquity have made them the subject of intense investigation regarding their nanoscale dynamics with increasing interest in obtaining sufficient temporalmore » and spatial resolution to directly observe nanoscale processes. However, the vast majority of experimental methods involve either bulk-averaging techniques including light, neutron, and X-ray scattering, or are static in nature including even the most advanced cryogenic transmission electron microscopy techniques. Here, we employ in situ liquid-cell transmission electron microscopy (LCTEM) to directly observe the evolution of individual amphiphilic block copolymer micellar nanoparticles in solution, in real time with nanometer spatial resolution. These observations, made on a proof-of-concept bioconjugate polymer amphiphile, revealed growth and evolution occurring by unimer addition processes and by particle-particle collision-and-fusion events. The experimental approach, combining direct LCTEM observation, quantitative analysis of LCTEM data, and correlated in silico simulations, provides a unique view of solvated soft matter nanoassemblies as they morph and evolve in time and space, enabling us to capture these phenomena in solution.« less

Temperature Effect on Micelle Formation: Molecular Thermodynamic Model Revisited.

PubMed

Khoshnood, Atefeh; Lukanov, Boris; Firoozabadi, Abbas

2016-03-08

Temperature affects the aggregation of macromolecules such as surfactants, polymers, and proteins in aqueous solutions. The effect on the critical micelle concentration (CMC) is often nonmonotonic. In this work, the effect of temperature on the micellization of ionic and nonionic surfactants in aqueous solutions is studied using a molecular thermodynamic model. Previous studies based on this technique have predicted monotonic behavior for ionic surfactants. Our investigation shows that the choice of tail transfer energy to describe the hydrophobic effect between the surfactant tails and the polar solvent molecules plays a key role in the predicted CMC. We modify the tail transfer energy by taking into account the effect of the surfactant head on the neighboring methylene group. The modification improves the description of the CMC and the predicted micellar size for aqueous solutions of sodium n-alkyl sulfate, dodecyl trimethylammonium bromide (DTAB), and n-alkyl polyoxyethylene. The new tail transfer energy describes the nonmonotonic behavior of CMC versus temperature. In the DTAB-water system, we redefine the head size by including the methylene group, next to the nitrogen, in the head. The change in the head size along with our modified tail transfer energy improves the CMC and aggregation size prediction significantly. Tail transfer is a dominant energy contribution in micellar and microemulsion systems. It also promotes the adsorption of surfactants at fluid-fluid interfaces and affects the formation of adsorbed layer at fluid-solid interfaces. Our proposed modifications have direct applications in the thermodynamic modeling of the effect of temperature on molecular aggregation, both in the bulk and at the interfaces.

Organised surfactant assemblies in analytical atomic spectrometry

NASA Astrophysics Data System (ADS)

Sanz-Medel, Alfredo; Fernandez de la Campa, Maria del Rosario; Gonzalez, Elisa Blanco; Fernandez-Sanchez, Maria Luisa

1999-02-01

The use of surfactant-based organised assemblies in analytical atomic spectroscopy is extensively and critically reviewed along three main lines: first, the ability of organised media to enhance detection of atomic spectroscopic methods by favourable manipulation of physical and chemical properties of the sample solution second, the extension of separation mechanisms by resorting to organised media and third a discussion of synergistic combinations of liquid chromatography separations and atomic detectors via the use of vesicular mobile phases. Changes in physical properties of sample solutions aspirated in atomic spectrometry by addition of surfactants can be advantageously used in at least four different ways: (i) to improve nebulisation efficiency; (ii) to enhance wettability of solid surfaces used for atomisation; (iii) to improve compatibility between aqueous and organic phases; and (iv) to achieve good dispersion of small particles in "slurry" techniques. Controversial results and statements published so far are critically discussed. The ability of surfactant-based organised assemblies, such as micelles and vesicles, to organise reactants at the molecular level has also been applied to enhance the characteristics of chemical generation of volalite species of metals and semi-metals (e.g., hydride or ethylide generation of As, Pb, Cd, Se, Sn, and cold vapour Hg generation) used in atomic methods. Enhancements in efficiency/transport of volatile species, increases in the reaction kinetics, stabilisation of some unstable species and changes in the selectivity of the reactions by surfactants are dealt with. Non-chromatographic cloud-point separations to design pre-concentration procedures with subsequent metal determination by atomic methods are addressed along with chromatographic separations of expanded scope by addition of surfactants to the conventional aqueous mobile phases of reversed-phase high-performance liquid chromatography. Finally, the synergistic effect of using vesicles to improve both the separation capabilities of reversed-phase HPLC and the detectability of atomic detectors by on-line vesicular hydride generation is described. In particular, the possible separation mechanisms responsible for micellar and vesicular mobile phases in reversed-phase chromatographies are analysed and compared. The possible effect of modification of stationary phases by monomers of the surfactants should also be taken into account. The application of such on-line couplings to develop new hybrid approaches to tackle modern problems of trace element speciation for As, Hg, Se, and Cd completes this revision of the present interface between analytical atomic spectroscopy and surfactant-based organised assemblies.

Exploring the Phase Behavior of Monoolein/Oleic Acid/Water Systems for Enhanced Donezepil Administration for Alzheimer Disease Treatment.

PubMed

Ruela, André Luís Morais; Carvalho, Flávia Chiva; Pereira, Gislaine Ribeiro

2016-01-01

Donepezil is a drug usually administered by oral route for Alzheimer disease treatment, but several gastric side effects have been reported as diarrhea, nausea, and anorexia. We explored the phase behavior of lyotropic liquid crystalline (LLC) mesophases composed by monoolein/oleic acid/water for enhanced administration of donepezil. Polarized light microscopy suggested that these systems ranged from isotropic inverse micellar solutions (L2) to viscous and birefringent reverse hexagonal (HII) mesophases according to the amount of water in the ternary systems. Phase transition was observed from a L2 phase to HII mesophase after swelling studies, an interesting property to be explored as a precursor of LLC mesophases for mucosal administration that increases its viscosity in situ. Mucoadhesive properties of LLC mesophases were characterized using a texture analyzer indicating that these systems can have an increased residence time in the site of absorption. Donepezil-free base was incorporated in the evaluated formulations, and their in vitro release was controlled up to 24 h. The phase behavior of the systems demonstrated a great potential for enhanced donepezil administration once these mucoadhesive-controlled release formulations can incorporate the drug and prolong its release, possibly reducing its side effects. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Responsive copolymers for enhanced petroleum recovery. Quarterly progress report, March 21, 1995--June 22, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCormick, C.; Hester, R.

Advanced polymer systems that possess microstructural features that are responsive to temperature, electrolyte concentration, and shear conditions are being synthesized which will be superior to polymers presently used for mobility control in enhanced oil recovery. Improved polymer performance is accomplished by controlling hydrophobic or ampholytic interactions between individual polymer chains in solution. Of special interest to our group have been (1) the elucidation of the mechanism of associative thickening and (2) the tailoring of thickeners with reversible associations responsive to changes in pH, ionic strength, temperature, or shear stress. A polymerization technique, termed ``micellar`` polymerization utilizes a surfactant to solubilizemore » a relatively low mole percent of a hydrophobic monomer in water for copolymerization with a hydrophilic monomer. In this report, we examine the role of surfactant-to-monomer ratio (SMR) in the reaction medium on microstructure utilizing the N-[(1- pyrenylsulfonamido)ethyl] acrylamide (APS) monomer as a fluorescent label. Comparison is made with previously reported terpolymers of identical AM/AA compositions with N-(4-decyl)phenylacrylamide as the hydrophobic monomer. Unlike the uncharged copolymer of AM/APS, however, the AM/AA/APS terpolymers of this study do not show intermolecular associative thickening, apparently due to insufficient liaisons of hydrophobic microdomains even at high concentrations of terpolymer.« less

Micellar electrokinetic chromatography with acid labile surfactant.

PubMed

Stanley, Bob; Lucy, Charles A

2012-02-24

We present a study of a degradable surfactant, sodium 4-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl)methoxy]-1-propane sulfonate that is also known as an acid-labile surfactant (ALS). The performance of ALS as a pseudostationary phase is assessed and compared with established pseudostationary phases such as sodium dodecyl sulphate (SDS), volatile surfactants and polymeric micelles. ALS achieves separation efficiency of 100,000-145,000 theoretical plates and relative standard deviation (RSD) of electrophoretic mobility (n=5) of less than 3%. Retention factors with ALS are strongly correlated with those with SDS. This is shown by the R2=0.79 for all eleven analytes and an R2=0.992 for specifically the non-hydrogen bonding (NHB) analytes. However, ALS displays different selectivity than SDS for hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) solutes (R2 of 0.74 and 0.88, respectively). ALS is degraded to less surface active compounds in acidic solution. These less surface-active compounds are more compatible with the electrospray ionization mass spectrometry (ESI-MS). ALS has a half-life of 48 min at pH 4. ALS has the potential to couple micellar electrokinetic chromatography (MEKC) with the ESI-MS. ALS can be used as a pseudostationary phase for a high efficiency separation and later acid hydrolyzed to enable an ESI-MS analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

Polymeric micellar pH-sensitive drug delivery system for doxorubicin.

PubMed

Hrubý, Martin; Konák, Cestmír; Ulbrich, Karel

2005-03-02

A novel polymeric micellar pH-sensitive system for delivery of doxorubicin (DOX) is described. Polymeric micelles were prepared by self-assembly of amphiphilic diblock copolymers in aqueous solutions. The copolymers consist of a biocompatible hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic block containing covalently bound anthracycline antibiotic DOX. The starting block copolymers poly(ethylene oxide)-block-poly(allyl glycidyl ether) (PEO-PAGE) with a very narrow molecular weight distribution (Mw/Mn ca. 1.05) were prepared by anionic ring opening polymerization using sodium salt of poly(ethylene oxide) monomethyl ether as macroinitiator and allyl glycidyl ether as functional monomer. The copolymers were covalently modified via reactive double bonds by the addition of methyl sulfanylacetate. The resulting ester subsequently reacted with hydrazine hydrate yielding polymer hydrazide. The hydrazide was coupled with DOX yielding pH-sensitive hydrazone bonds between the drug and carrier. The resulting conjugate containing ca. 3 wt.% DOX forms micelles with Rh(a)=104 nm in phosphate-buffered saline. After incubation in buffers at 37 degrees C DOX was released faster at pH 5.0 (close to pH in endosomes; 43% DOX released within 24 h) than at pH 7.4 (pH of blood plasma; 16% DOX released within 24 h). Cleavage of hydrazone bonds between DOX and carrier continues even after plateau in the DOX release from micelles incubated in aqueous solutions is reached.

Development and characterization of morin hydrate-loaded micellar nanocarriers for the effective management of Alzheimer's disease.

PubMed

Singh, Manpreet; Thakur, Vandana; Deshmukh, Rahul; Sharma, Amit; Rathore, M S; Kumar, Ajay; Mishra, Neeraj

2018-03-01

The aim of this study was to prepare and characterise oral delivery of morin hydrate-loaded micellar nanocarriers using Pluronic P127 and Pluronic F123 for the effective management of Alzheimer's disease. After administration of formulation brain and blood drug concentration were found to be highest for optimised morin hydrate-loaded micellar nanocarriers as compared to plain morin hydrate. Significant (p < 0.05) reduction in assessed pharmacodynamic parameters was observed after administration of morin hydrate-loaded micellar nanocarriers as compared to disease control group. Chronic treatment with morin-loaded micelles significantly increased the memory in AlCl 3 induced Alzheimer's disease in Wistar rats.

Effect of tartarate and citrate based food additives on the micellar properties of sodium dodecylsulfate for prospective use as food emulsifier.

PubMed

Banipal, Tarlok S; Kaur, Harjinder; Kaur, Amanpreet; Banipal, Parampaul K

2016-01-01

Citrate and tartarate based food preservatives can be used to enhance the emulsifying properties of sodium dodecylsulfate (SDS) based micellar system and thus making it appropriate for food applications. Exploration of interactions between the two species is the key constraint for execution of such ideas. In this work various micellar and thermodynamic parameters of SDS like critical micellar concentration (CMC), standard Gibbs free energy of micellization (ΔG(0)mic.) etc. have been calculated in different concentrations of disodium tartarate (DST) and trisodium citrate (TSC) in the temperature range (288.15-318.15)K from the conductivity and surface tension measurements. The parameters obtained from these studies reveal the competitive nature of both the additives with SDS for available positions at the air/water interface. TSC is found to be more effective additive in order to make SDS micellar system better for its potential applications as food emulsifier. Copyright © 2015 Elsevier Ltd. All rights reserved.

Anisotropy Changes of a Fluorescent Probe during the Micellar Growth and Clouding of a Nonionic Detergent.

PubMed

Komaromy-Hiller; von Wandruszka R

1996-01-15

The effects of temperature and Triton X-114 (TX-114) concentration on the fluorescence anisotropy of perylene were investigated before and after detergent clouding. The measured anisotropy values were used to estimate the microviscosity of the micellar interior. In the lower detergent concentration range, an anisotropy maximum was observed at the critical micelle concentration (CMC), while the values decreased in the range immediately above the CMC. This was ascribed to the micellar volume increase, which, in the case of TX-114, was not accompanied by a more ordered internal environment. A gradual decrease of anisotropy and microviscosity with increasing temperature below the cloud point was observed. At the cloud point, no abrupt changes were found to occur. Compared to detergents with more flexible hydrophobic moieties, TX-114 micelles have a relatively ordered micellar interior indicated by the microviscosity and calculated fusion energy values. In the separated micellar phase formed after clouding, the probe anisotropy increased as water was eliminated at higher temperatures.

Oil recovery method using high water content oil-external micellar dispersions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.; Roszelle, W.O.; Svaldi, M.A.

1971-10-19

A high water content oil-external micellar dispersion (containing 55 percent to about 90 percent water) was developed for enhanced oil recovery. The micellar slug contained petroleum sulfonate (molecular weight averaged at about 350 to about 525), hydrocarbon, water and cosurfactant. The micellar slug was driven by a mobility buffer slug, which consisted of No. 530 Pusher, fusel oil and the residue Palestine water (420 ppm TDS) from the Palestine water reservoir in Palestine, Illinois. Fired Berea sandstone cores (porosity near 20 percent) were saturated with water (18,000 ppm sodium chloride), flooded with sweet black crude oil from Henry lease inmore » Illinois (7 cp at 72/sup 0/F), and waterflooded with water from Henry lease (18,000 ppm TDS). A maximum recovery of 11.5 percent of oil in place was recovered by 2 percent pore volume of a micellar dispersion containing petroleum sulfonate (MW 406), 70 percent by volume distilled water, and p-hexanol.« less

High water content oil-external micellar dispersions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.; Roszelle, W.O.; Svaldi, M.A.

1970-02-24

A high water content oil-external micellar dispersion (containing 55 percent to about 90 percent water) was developed for enhanced oil recovery. The micellar slug contained petroleum sulfonate (molecular weight averaged at about 350 to about 525), hydrocarbon, water and cosurfactant. The micellar slug was driven by a mobility buffer slug, which consisted of No. 530 Pusher, fusel oil and the residue Palestine water (420 ppm TDS) from the Palestine water reservoir in Palestine, Illinois. Fired Berea sandstone cores (porosity near 20 percent) were saturated with water (18,000 ppm sodium chloride), flooded with sweet black crude oil from Henry lease inmore » Illinois (7 cp at 72/sup 0/F), and waterflooded with water from Henry lease (18,000 ppm TDS). A maximum recovery of 11.5 percent of oil in place was recovered by 2 percent pore volume of a micellar dispersion containing petroleum sulfonate (MW 406), crude oil, 70 percent by volume distilled water, and p-hexanol.« less

A facile strategy for fine-tuning the stability and drug release of stimuli-responsive cross-linked micellar nanoparticles towards precision drug delivery.

PubMed

Xiao, Kai; Lin, Tzu-Yin; Lam, Kit S; Li, Yuanpei

2017-06-14

Precision drug delivery has a great impact on the application of precision oncology for better patient care. Here we report a facile strategy for fine-tuning the stability, drug release and responsiveness of stimuli-responsive cross-linked nanoparticles towards precision drug delivery. A series of micellar nanoparticles with different levels of intramicellar disulfide crosslinkages could be conveniently produced with a mixed micelle approach. These micellar nanoparticles were all within a size range of 25-40 nm so that they could take full advantage of the enhanced permeability and retention (EPR) effect for tumor-targeted drug delivery. The properties of these nanoparticles such as critical micelle concentration (CMC), stability, drug release and responsiveness to a reductive environment could be well correlated with the levels of crosslinking (LOC). Compared to the micellar nanoparticles with a LOC at 0% that caused the death of animals of two species (mouse and rat) due to the acute toxicity such as hemolysis, the nanoparticles at all other levels of crosslinking were much safer to be administered into animals. The in vitro antitumor efficacy of micellar nanoparticles crosslinked at lower levels (20% & 50%) were much more effective than that of 100% crosslinked micellar nanoparticles in SKOV-3 ovarian cancer cells.

Selection of reservoirs amenable to micellar flooding. First annual report, October 1978-December 1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldburg, A.; Price, H.

The overall project objective is to build a solid engineering base upon which the Department of Energy (DOE) can improve and accelerate the application of micellar-polymer recovery technology to Mid-Continent and California sandstone reservoirs. The purpose of the work carried out under these two contracts is to significantly aid, both DOE and the private sector, in gaining the following Project Objectives: to select the better micellar-polymer prospects in the Mid-Continent and California regions; to assess all of the available field and laboratory data which has a bearing on recovering oil by micellar-polymer projects in order to help identify and resolvemore » both the technical and economic constraints relating thereto; and to design and analyze improved field pilots and tests and to develop a micellar-polymer applications matrix for use by the potential technology users; i.e., owner/operators. The report includes the following: executive summary and project objectives; development of a predictive model for economic evaluation of reservoirs; reservoir data bank for micellar-polymer recovery evaluation; PECON program for preliminary economic evaluation; ordering of candidate reservoirs for additional data acquisition; validation of predictive model by numerical simulation; and work forecast. Tables, figures and references are included.« less

Reverse micelle-loaded lipid nano-emulsions: new technology for nano-encapsulation of hydrophilic materials.

PubMed

Anton, Nicolas; Mojzisova, Halina; Porcher, Emilien; Benoit, Jean-Pierre; Saulnier, Patrick

2010-10-15

This study presents novel, recently patented technology for encapsulating hydrophilic species in lipid nano-emulsions. The method is based on the phase-inversion temperature method (the so-called PIT method), which follows a low-energy and solvent-free process. The nano-emulsions formed are stable for months, and exhibit droplet sizes ranging from 10 to 200 nm. Hydrophilic model molecules of fluorescein sodium salt are encapsulated in the oily core of these nano-emulsion droplets through their solubilisation in the reverse micellar system. As a result, original, multi-scaled nano-objects are generated with a 'hydrophilic molecule in a reverse-micelles-in-oil-in-water' structure. Once fluorescein has been encapsulated it remains stable, for thermodynamic reasons, and the encapsulation yields can reach 90%. The reason why such complex objects can be formed is due to the soft method used (PIT method) which allows the conservation of the structure of the reverse micelles throughout the formulation process, up to their entrapment in the nano-emulsion droplets. In this study, we focus the investigation on the process itself, revealing its potential and limits. Since the formulation of nanocarriers for the encapsulation of hydrophilic substances still remains a challenge, this study may constitute a significant advance in this field. Copyright 2010 Elsevier B.V. All rights reserved.

Micellar casein concentrate production with a 3X, 3-stage, uniform transmembrane pressure ceramic membrane process at 50°C.

PubMed

Hurt, E; Zulewska, J; Newbold, M; Barbano, D M

2010-12-01

The production of serum protein (SP) and micellar casein from skim milk can be accomplished using microfiltration (MF). Potential commercial applications exist for both SP and micellar casein. Our research objective was to determine the total SP removal and SP removal for each stage, and the composition of retentates and permeates, for a 3×, continuous bleed-and-feed, 3-stage, uniform transmembrane pressure (UTP) system with 0.1-μm ceramic membranes, when processing pasteurized skim milk at 50°C with 2 stages of water diafiltration. For each of 4 replicates, about 1,100 kg of skim milk was pasteurized (72°C, 16s) and processed at 3× through the UTP MF system. Retentate from stage 1 was cooled to <4°C and stored until the next processing day, when it was diluted with reverse osmosis water back to a 1× concentration and again processed through the MF system (stage 2) to a 3× concentration. The retentate from stage 2 was stored at <4°C, and, on the next processing day, was diluted with reverse osmosis water back to a 1× concentration, before running through the MF system at 3× for a total of 3 stages. The retentate and permeate from each stage were analyzed for total nitrogen, noncasein nitrogen, and nonprotein nitrogen using Kjeldahl methods; sodium dodecyl sulfate-PAGE analysis was also performed on the retentates from each stage. Theoretically, a 3-stage, 3× MF process could remove 97% of the SP from skim milk, with a cumulative SP removal of 68 and 90% after the first and second stages, respectively. The cumulative SP removal using a 3-stage, 3× MF process with a UTP system with 0.01-μm ceramic membranes in this experiment was 64.8 ± 0.8, 87.8 ± 1.6, and 98.3 ± 2.3% for the first, second, and third stages, respectively, when calculated using the mass of SP removed in the permeate of each stage. Various methods of calculation of SP removal were evaluated. Given the analytical limitations in the various methods for measuring SP removal, calculation of SP removal based on the mass of SP in the skim milk (determined by Kjeldahl) and the mass SP present in all of the permeate produced by the process (determined by Kjeldahl) provided the best estimate of SP removal for an MF process. Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Determination of the critical micelle concentration in simulations of surfactant systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santos, Andrew P.; Panagiotopoulos, Athanassios Z., E-mail: azp@princeton.edu

Alternative methods for determining the critical micelle concentration (cmc) are investigated using canonical and grand canonical Monte Carlo simulations of a lattice surfactant model. A common measure of the cmc is the “free” (unassociated) surfactant concentration in the presence of micellar aggregates. Many prior simulations of micellizing systems have observed a decrease in the free surfactant concentration with overall surfactant loading for both ionic and nonionic surfactants, contrary to theoretical expectations from mass-action models of aggregation. In the present study, we investigate a simple lattice nonionic surfactant model in implicit solvent, for which highly reproducible simulations are possible in bothmore » the canonical (NVT) and grand canonical (μVT) ensembles. We confirm the previously observed decrease of free surfactant concentration at higher overall loadings and propose an algorithm for the precise calculation of the excluded volume and effective concentration of unassociated surfactant molecules in the accessible volume of the solution. We find that the cmc can be obtained by correcting the free surfactant concentration for volume exclusion effects resulting from the presence of micellar aggregates. We also develop an improved method for determination of the cmc based on the maximum in curvature for the osmotic pressure curve determined from μVT simulations. Excellent agreement in cmc and other micellar properties between NVT and μVT simulations of different system sizes is observed. The methodological developments in this work are broadly applicable to simulations of aggregating systems using any type of surfactant model (atomistic/coarse grained) or solvent description (explicit/implicit)« less

Jet A fuel recovery using micellar flooding: Design and implementation.

PubMed

Kostarelos, Konstantinos; Lenschow, Søren R; Stylianou, Marinos A; de Blanc, Phillip C; Mygind, Mette Marie; Christensen, Anders G

2016-09-01

Surfactants offer two mechanisms for recovering NAPLs: 1) to mobilize NAPL by reducing NAPL/water interfacial tension, and; 2) to increase the NAPL's aqueous solubility-called solubilization-as an enhancement to pump & treat. The second approach has been well-studied and applied successfully in several pilot-scale and a few full-scale tests within the last 15years, known as Surfactant Enhanced Aquifer Remediation (SEAR). A useful source of information for this second approach is the "Surfactant-enhanced aquifer remediation (SEAR) design manual" from the U.S. Navy Facilities Engineering Command. Few attempts, however, have been made at recovering NAPLs using the mobilization approach presented in this paper. Now, a full-scale field implementation of the mobilization approach is planned to recover an LNAPL (Jet A fuel) from a surficial sand aquifer located in Denmark using a smaller amount of surfactant solution and fewer PVs of throughput compared with the SEAR approach. The approach will rely on mobilizing the LNAPL so that it is recovered ahead of the surfactant microemulsion, also known as a micellar flood. This paper will review the laboratory work performed as part of the design for a full-scale implementation of a micellar flood. Completed lab work includes screening of surfactants, phase behavior and detailed salinity scans of the most promising formulations, and generating a ternary diagram to be used for the numerical simulations of the field application. The site owners and regulators were able to make crucial decisions such as the anticipated field results based on this work. Copyright © 2016 Elsevier B.V. All rights reserved.

The chemical interpretation and practice of linear solvation energy relationships in chromatography.

PubMed

Vitha, Mark; Carr, Peter W

2006-09-08

This review focuses on the use of linear solvation energy relationships (LSERs) to understand the types and relative strength of the chemical interactions that control retention and selectivity in the various modes of chromatography ranging from gas chromatography to reversed phase and micellar electrokinetic capillary chromatography. The most recent, widely accepted symbolic representation of the LSER model, as proposed by Abraham, is given by the equation: SP=c + eE + sS + aA + bB + vV, in which, SP can be any free energy related property. In chromatography, SP is most often taken as logk' where k' is the retention factor. The letters E, S, A, B, and V denote solute dependent input parameters that come from scales related to a solute's polarizability, dipolarity (with some contribution from polarizability), hydrogen bond donating ability, hydrogen bond accepting ability, and molecular size, respectively. The e-, s-, a-, b-, and v-coefficients and the constant, c, are determined via multiparameter linear least squares regression analysis of a data set comprised of solutes with known E, S, A, B, and V values and which span a reasonably wide range in interaction abilities. Thus, LSERs are designed to probe the type and relative importance of the interactions that govern solute retention. In this review, we include a synopsis of the various solvent and solute scales in common use in chromatography. More importantly, we emphasize the development and physico-chemical basis of - and thus meaning of - the solute parameters. After establishing the meaning of the parameters, we discuss their use in LSERs as applied to understanding the intermolecular interactions governing various gas-liquid and liquid-liquid phase equilibria. The gas-liquid partition process is modeled as the sum of an endoergic cavity formation/solvent reorganization process and exoergic solute-solvent attractive forces, whereas the partitioning of a solute between two solvents is thermodynamically equivalent to the difference in two gas/liquid solution processes. We end with a set of recommendations and advisories for conducting LSER studies, stressing the proper chemical and statistical application of the methodology. We intend that these recommendations serve as a guide for future studies involving the execution, statistical evaluation, and chemical interpretation of LSERs.

Small angle neutron scattering study of sodium dodecyl sulfate micellar growth driven by addition of a hydrotropic salt.

PubMed

Hassan, P A; Fritz, Gerhard; Kaler, Eric W

2003-01-01

The structures of aggregates formed in aqueous solutions of an anionic surfactant, sodium dodecyl sulfate (SDS), with the addition of a cationic hydrotropic salt, p-toluidine hydrochloride (PTHC), have been investigated by small angle neutron scattering (SANS). The SANS spectra exhibit a pronounced peak at low salt concentration, indicating the presence of repulsive intermicellar interactions. Model-independent real space information about the structure is obtained from a generalized indirect Fourier transformation (GIFT) technique in combination with a suitable model for the interparticle structure factor. The interparticle interaction is captured using the rescaled mean spherical approximation (RMSA) closure relation and a Yukawa form of the interaction potential. Further quantification of the geometrical parameters of the micelles was achieved by a complete fit of the SANS data using a prolate ellipsoidal form factor and the RMSA structure factor. The present study shows that PTHC induces a decrease in the fractional charge of the micelles due to adsorption at the micellar surface and consequent growth of the SDS micelles from nearly globular to rodlike as the concentration of PTHC increases.

Lipid-absorbing Polymers

NASA Technical Reports Server (NTRS)

Marsh, H. E., Jr.; Wallace, C. J.

1973-01-01

The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.

Electrochemistry in Colloids and Dispersions. Volume 1. Electroanalytical Methods and Applications, Electrosynthesis and Electrocatalysis, Polymers and Latexes

DTIC Science & Technology

1992-02-04

derived from dissociation of surface acid groups of the microparticles. The surface charges of these particles are provided by sulfate groups... sulfate micellar solution as a function of electrolyte concentration3 Jon R. Kirchhoff, John D. Skelton, Jr., and Kregg T. Brooks Department of...films on the voltamnmetric curve obtained for the oxidation of benzilic acid on a platinum anode in 2M sodium hydroxide. The acid is soluble in this

Ion dehydration controls adsorption at the micellar interface: hydrotropic ions.

PubMed

Lima, Filipe S; Andrade, Marcos F C; Mortara, Laura; Gustavo Dias, Luís; Cuccovia, Iolanda M; Chaimovich, Hernan

2017-11-22

The properties of ionic micelles depend on the nature of the counterion, and these effects become more evident as the ion adsorption at the interface increases. Prediction of the relative extent of ion adsorption is required for rational design of ionic micellar aggregates. Unlike the well understood adsorption of monatomic ions, the adsorption of polyatomic ions is not easily predicted. We combined experimental and computational methods to evaluate the affinity of hydrotropic ions, i.e., ions with polar and apolar regions, to the surface of positively charged micelles. We analyzed cationic micelles of dodecyltrimethylammonium and six hydrotropic counterions: methanesulfonate, trifluoromethanesulfonate, benzenesulfonate, acetate, trifluoroacetate and benzoate. Our results demonstrated that the apolar region of hydrotropic ions had the largest influence on micellar properties. The dehydration of the apolar region of hydrotropic ions upon their adsorption at the micellar interface determined the ion adsorption extension, differently to what was expected based on Collins' law of matching affinities. These results may lead to more general models to describe the adsorption of ions, including polyatomic ions, at the micellar interface.

Sans study of reverse micelles formed upon extraction of inorganic acids by TBP in n-octane.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiarizia, R.; Briand, A.; Jensen, M. P.

2008-01-01

Small-angle neutron scattering (SANS) data for n-octane solutions of TBP loaded with progressively larger amounts of HNO{sub 3}, HClO{sub 4}, H{sub 2}SO{sub 4}, and H{sub 3}PO{sub 4} up to and beyond the LOC (limiting organic concentration of acid) condition, were interpreted using the Baxter model for hard spheres with surface adhesion. The coherent picture of the behavior of the TBP solutions derived from the SANS investigation discussed in this paper confirmed our recently developed model for third phase formation. This model analyses the features of the scattering data in the low Q region as arising from van der Waals interactionsmore » between the polar cores of reverse micelles. Our SANS data indicated that the TBP micelles swell when acid and water are extracted into their polar core. The swollen micelles have critical diameters ranging from 15 to 22 {angstrom}, and polar core diameters between 10 and 15 {angstrom}, depending on the specific system. At the respective LOC conditions, the TBP weight-average aggregation numbers are -4 for HClO{sub 4}, -6 for H2SO{sub 4}, -7 for HCl, and -10 for H{sub 3}PO{sub 4}. The comparison between the behavior of HNO{sub 3}, a non-third phase forming acid, and the other acids provided an explanation of the effect of the water molecules present in the polar core of the micelles on third phase formation. The thickness of the lipophilic shell of the micelles indicated that the butyl groups of TBP lie at an angle of -25 degrees relative to a plane tangent to the micellar core. The critical energy of intermicellar attraction, U(r), was about -2 k{sub B}T for all the acids investigated. This value is the same as that reported in our previous publications on the extraction of metal nitrates by TBP, confirming that the same mechanism and energetics are operative in the formation of a third phase, independent of whether the chemical species extracted are metal nitrate salts or inorganic acids.« less

A Novel Micellar Electrokinetic Chromatographic Method for Separation of Metal-DDTC Complexes

PubMed Central

Mallah, Arfana; Memon, Saima Q.; Solangi, Amber R.; Memon, Najma; Abbassi, Kulsoom; Khuhawar, Muhammad Yar

2012-01-01

Micellar electrokinetic chromatography (MEKC) was examined for the separation and determination of Mo(VI), Cr(VI), Ni(II), Pd(II), and Co(III) as diethyl dithiocarbamate (DDTC) chelates. The separation was achieved from fused silica capillary (52 cm × 75 μm id) with effective length 40 cm, background electrolyte (BGE) borate buffer pH 9.1 (25 mM), CTAB 30% (100 mM), and 1% butanol in methanol (70 : 30 : 5 v/v/v) with applied voltage of −10 kV using reverse polarity. The photodiode array detection was achieved at 225 nm. The linear calibration for each of the element was obtained within 0.16–10 μg/mL with a limit of detection (LOD) 0.005–0.0167 μg/mL. The separation and determination was repeatable with relative standard deviation (RSD) within 2.4–3.3% (n = 4) in terms of migration time and peak height/peak area. The method was applied for the determination of Mo(VI) from potatoes and almond, Ni(II) from hydrogenated vegetable oil, and Co(III) from pharmaceutical preparations with RSD within 3.9%. The results obtained were checked by standard addition and rechecked by atomic absorption spectrometry. PMID:22649320

Micellar Polymer Encapsulation of Enzymes.

PubMed

Besic, Sabina; Minteer, Shelley D

2017-01-01

Although enzymes are highly efficient and selective catalysts, there have been problems incorporating them into fuel cells. Early enzyme-based fuel cells contained enzymes in solution rather than immobilized on the electrode surface. One problem utilizing an enzyme in solution is an issue of transport associated with long diffusion lengths between the site of bioelectrocatalysis and the electrode. This issue drastically decreases the theoretical overall power output due to the poor electron conductivity. On the other hand, enzymes immobilized at the electrode surface have eliminated the issue of poor electron conduction due to close proximity of electron transfer between electrode and the biocatalyst. Another problem is inefficient and short term stability of catalytic activity within the enzyme that is suspended in free flowing solution. Enzymes in solutions are only stable for hours to days, whereas immobilized enzymes can be stable for weeks to months and now even years. Over the last decade, there has been substantial research on immobilizing enzymes at electrode surfaces for biofuel cell and sensor applications. The most commonly used techniques are sandwich or wired. Sandwich techniques are powerful and successful for enzyme immobilization; however, the enzymes optimal activity is not retained due to the physical distress applied by the polymer limiting its applications as well as the non-uniform distribution of the enzyme and the diffusion of analyte through the polymer is slowed significantly. Wired techniques have shown to extend the lifetime of an enzyme at the electrode surface; however, this technique is very hard to master due to specific covalent bonding of enzyme and polymer which changes the three-dimensional configuration of enzyme and with that decreases the optimal catalytic activity. This chapter details encapsulation techniques where an enzyme will be immobilized within the pores/pockets of the hydrophobically modified micellar polymers such as Nafion ® and chitosan. This strategy has been shown to safely immobilize enzymes at electrode surfaces with storage and continuous operation lifetime of more than 2 years.

A simplified radiometabolite analysis procedure for PET radioligands using a solid phase extraction with micellar medium.

PubMed

Nakao, Ryuji; Halldin, Christer

2013-07-01

A solid phase extraction method has been developed for simple and high-speed direct determination of PET radioligands in plasma. This methodology makes use of a micellar medium and a solid-phase extraction cartridge for displacement of plasma protein bound radioligand and separation of PET radioligands from their radiometabolites without significant preparation. The plasma samples taken from monkey or human during PET measurements were mixed with a micellar eluent containing an anionic surfactant sodium dodecyl sulphate and loaded onto SPE cartridges. The amount of radioactivity corresponding to parent radioligand (retained on the cartridge) and its radioactive metabolites (eluted with micellar eluent) was measured. Under the optimized conditions, excellent separation of target PET radioligands from their radiometabolites was achieved with a single elution and short run-time of 1 min. This method was successfully applied to study the metabolism for (11)C-labelled radioligands in human or monkey plasma. The amount of parent PET radioligands estimated by micellar solid phase extraction strongly corresponded with that determined by radio-LC. The improved throughput permitted the analysis of a large number of plasma samples (up to 13 samples per one PET study) for accurate estimation of metabolite-corrected input function during quantitative PET imaging studies. Solid phase extraction together with micellar medium is fast, sensitive and easy to use, and therefore it is an attractive alternative method to determine relative composition of PET radioligands in plasma. Copyright © 2013 Elsevier Inc. All rights reserved.

Characterization of chlorophyll derivatives in micelles of polymeric surfactants aiming photodynamic applications

NASA Astrophysics Data System (ADS)

Gerola, Adriana Passarella; de Morais, Flavia Amanda Pedroso; Costa, Paulo Fernando A.; Kimura, Elza; Caetano, Wilker; Hioka, Noboru

2017-02-01

The spectrophotometric properties of chlorophylls' derivatives (Chls) formulated in the Pluronics® F-127 and P-123 were evaluated and the results have shown that the Chls were efficiently solubilized in these drug delivery systems as monomers. The relative location of the Chls in the Pluronics® was estimated from the Stokes shift and micropolarity of the micellar environment. Chls with phytyl chain were located in the micellar core, where the micropolarity is similar to ethanol, while phorbides' derivatives (without phytyl chain) were located in the outer shell of the micelle, i.e., more polar environment. In addition, the thermal stability of the micellar formulations was evaluated through electronic absorption, fluorescence emission and resonance light scattering with lowering the temperature. The Chls promote the stability of the micelles at temperatures below the Critical Micellar Temperature (CMT) of these surfactants. For F-127 formulations, the water molecules drive through inside the nano-structure at temperatures below the CMT, which increased the polarity of this microenvironment and directly affected the spectrophotometric properties of the Chls with phytyl chain. The properties of the micellar microenvironment of P-123, with more hydrophobic core due to the small PEO/PPO fraction, were less affected by lowering the temperature than for F-127. These results enable us to better understand the Chls behavior in micellar copolymers and allowed us to design new drug delivery system that maintains the photosensitizer's properties for photodynamic applications.

Controlling Molecular Ordering in Solution-State Conjugated Polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Jiahua; Han, Youngkyu; Kumar, Rajeev

Rationally encoding molecular interactions that can control the assembly structure and functional expression in solution of conjugated polymers holds great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution,more » we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.« less

Controlling Molecular Ordering in Solution-State Conjugated Polymers

DOE PAGES

Zhu, Jiahua; Han, Youngkyu; Kumar, Rajeev; ...

2015-07-17

Rationally encoding molecular interactions that can control the assembly structure and functional expression in solution of conjugated polymers holds great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution,more » we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.« less

Effect of electrostatic interaction on the location of molecular probe in polymer-surfactant supramolecular assembly: a solvent relaxation study.

PubMed

Singh, Prabhat K; Kumbhakar, Manoj; Pal, Haridas; Nath, Sukhendu

2008-07-03

Effect of electrostatic interaction on the location of a solubilized molecular probe with ionic character in a supramolecular assembly composed of a triblock copolymer, P123 ((ethylene oxide) 20-(propylene oxide) 70-(ethylene oxide) 20) and a cosurfactant cetyltrimethylammonium chloride (CTAC) in aqueous medium has been studied using steady-state and time-resolved fluorescence measurements. Coumarin-343 dye in its anionic form has been used as the molecular probe. In the absence of the surfactant, CTAC, the probe C343 prefers to reside at the surface region of the P123 micelle, showing a relatively less dynamic Stokes' shift, as a large part of the Stokes' shift is missed in the present measurements due to faster solvent relaxation at micellar surface region. As the concentration of CTAC is increased in the solution, the percentage of the total dynamic Stokes' shift observed from time-resolved measurements gradually increases until it reaches a saturation value. Observed results have been rationalized on the basis of the mixed micellar structure of the supramolecular assembly, where the hydrocarbon chain of the CTAC surfactant dissolves into the nonpolar poly(propylene oxide) (PPO) core of the P123 micelle and the positively charged headgroup of CTAC resides at the interfacial region between the central PPO core and the surrounding hydrated poly(ethylene oxide) (PEO) shell or the corona region. The electrostatic attraction between the anionic probe molecule and the positively charged surface of the PPO core developed by the presence of CTAC results in a gradual shift of the probe in the deeper region of the micellar corona region with an increase in the CTAC concentration, as clearly manifested from the solvation dynamics results.

Temperature and anion responsive self-assembly of ionic liquid block copolymers coating gold nanoparticles

NASA Astrophysics Data System (ADS)

Li, Junbo; Zhao, Jianlong; Wu, Wenlan; Liang, Ju; Guo, Jinwu; Zhou, Huiyun; Liang, Lijuan

2016-06-01

In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)]- block-(N-isopropylacrylamide) (PMMPImB- b-PNIPAAm) was first synthesized by reversible additionfragmentation chain transfer (RAFT) and then attached on the surface of gold nanoparticles (Au NPs) via a strong gold-sulfur bonding for preparing hybrid nanoparticles (PMMPImB- b-PNIPAAm-@-Au NPs). The hybrid NPs had a three layers micelle-like structure, including a gold core, thermo-responsive inner shell and anion responsive outer corona. The self-assembling behavior of thermal- and anion-response from shell and corona were respectively investigated by change of temperature and addition of (CF3SO2)2N-. The results showed the hybrid NPs retained a stable dispersion beyond the lower critical solution temperature (LCST) because of the space or electrostatic protecting by outer PMMPImB. However, with increasing concentration of (CF3SO2)2N-, the micellization of self-assembling PMMPImB- b-PNIPAAm-@-Au NPs was induced to form micellar structure containing the core with hydrophobic PMMPImB-(CF3SO2)2N- surrounded by composite shell of Au NPs-PNIPAAm via the anionresponsive properties of ILBCs. These results indicated that the block copolymers protected plasmonic nanoparticles remain self-assembling properties of block copolymers when phase transition from outer corona polymer.

Influence of gold nanoparticles of varying size in improving the lipase activity within cationic reverse micelles.

PubMed

Maiti, Subhabrata; Das, Dibyendu; Shome, Anshupriya; Das, Prasanta Kumar

2010-02-08

Herein, we report the effect of gold nanoparticles (GNPs) in enhancing lipase activity in reverse micelles of cetyltrimethylammonium bromide (CTAB)/water/isooctane/n-hexanol. The size and concentration of the nanoparticles were varied and their specific roles were assessed in detail. An overall enhancement of activity was observed in the GNP-doped CTAB reverse micelles. The improvement in activity becomes more prominent with increasing concentration and size of the GNPs (0-52 microM and ca. 3-30 nm, respectively). The observed highest lipase activity (k(2)=1070+/-12 cm(3) g(-1) s(-1)) in GNP-doped CTAB reverse micelles ([GNP]: 52 microm, ca. 20 nm) is 2.5-fold higher than in CTAB reverse micelles without GNPs. Improvement in the lipase activity is only specific to the GNP-doped reverse micellar media, whereas GNP deactivates and structurally deforms the enzyme in aqueous media. The reason for this activation is probably due to the formation of larger-sized reverse micelles in which the GNP acts as a polar core and the surfactants aggregate around the nanoparticle ('GNP pool') instead of only water. Lipase at the augmented interface of the GNP-doped reverse micelle showed improved activity because of enhancement in both the substrate and enzyme concentrations and increased flexibility in the lipase conformation. The extent of the activation is greater in the case of the larger-sized GNPs. A correlation has been established between the activity of lipase and its secondary structure by using circular dichroism and FTIR spectroscopic analysis. The generalized influence of GNP is verified in the reverse micelles of another surfactant, namely, cetyltripropylammonium bromide (CTPAB). TEM, dynamic light scattering (DLS), and UV/Vis spectroscopic analysis were utilized to characterize the GNPs and the organized aggregates. For the first time, CTAB-based reverse micelles have been found to be an excellent host for lipase simply by doping with appropriately sized GNPs.

Small angle scattering from protein/sugar conjugates

NASA Astrophysics Data System (ADS)

Jackson, Andrew; White, John

2006-11-01

The Maillard reaction between free amine groups on proteins and sugars is well known. We have examined the effect of the reaction of the casein group of milk proteins with sugars on their nanoscale structure and aggregation. The small angle neutron scattering from beta casein and sodium caseinate and their sugar conjugates have been studied as a function of solution concentration. At high conjugate concentration (greater than ca. 5 mg/ml) the addition of sugar reduces supra-micellar aggregation of the protein whilst at lower concentration, where the protein is expected to be deaggregated already, little effect is seen. Guinier analysis of the scattering data show a radius of gyration of around 75 A˚ for beta casein in solution and around 80 A˚ for the sucrose conjugate.

Specific anion binding to sulfobetaine micelles and kinetics of nucleophilic reactions.

PubMed

Marte, Luisa; Beber, Rosane C; Farrukh, M Akhyar; Micke, Gustavo A; Costa, Ana C O; Gillitt, Nicholas D; Bunton, Clifford A; Di Profio, Pietro; Savelli, Gianfranco; Nome, Faruk

2007-08-23

With fully micellar bound substrates reactions of OH- with benzoic anhydride, Bz(2)O, and of Br- with methyl naphthalene-2-sulfonate, MeONs, in micellized sulfobetaines are strongly inhibited by NaClO4 which displaces the nucleophilic anions from the micellar pseudophases. Micellar incorporations of ClO4- and Br- are estimated with an ion-selective electrode and by electrophoresis, and partitioning of Br- between water and micelles is related to changes in NMR spectral (79)Br- line widths. Extents of inhibition by ClO4- of these nucleophilic reactions in the micellar pseudophase are related to quantitative displacement of the reactive anions from the micelles by ClO4-. The kinetic data are correlated with physical evidence on the strong interactions between sulfobetaines and ClO4-, which turn sulfobetaine micelles anionic and effectively provoke displacement of OH- and Br-.

Au/CdS Hybrid Nanoparticles in Block Copolymer Micellar Shells.

PubMed

Koh, Haeng-Deog; Changez, Mohammad; Lee, Jae-Suk

2010-10-18

A polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) micellar structure with a P2VP core containing 5 nm CdS nanoparticles (NPs) and a PS shell formed in toluene that is a good solvent for PS block undergoes the core-shell inversion by excess addition of methanol that is a good solvent for P2VP block. It leads to the formation of micellar shell-embedded CdS NPs in the methanol major phase. The spontaneous crystalline growth of Au NPs on the CdS surfaces positioned at micellar shells without a further reduction process is newly demonstrated. The nanostructure of Au/CdS/PS-b-P2VP hybrid NPs is confirmed by transmission electron microscopy, energy-dispersive X-ray, and UV-Vis absorption. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effective solubilization of chalcones in micellar phase: Conductivity and voltammetric study

NASA Astrophysics Data System (ADS)

Ahmed, Safeer; Khan, Gul Tiaz; Shah, Syed Sakhawat

2013-12-01

The solubilization of four chalcones, between aqueous and micellar phases of ionic surfactants (SDS and CTAB), was investigated by conductivity and cyclic voltammetry (CV) techniques. From conductivity data, a decrease in the critical micellar concentration (CMC) of the surfactants, in presence of the chalcones was ascribed to the decreased charge density over the surfactants. The results were seconded by thermodynamic parameters including degree of ionization (α), counter ion binding (β), and standard Gibbs free energy of micellization (Δ G {m/○}). The added surfactant decreased the peak current of the oxidized chalcone and shifted the peak potential either positively (in presence of SDS) or negatively (in presence of CTAB). The effect is rationalized as chalcone-surfactant interaction and quantitated as binding constant ( K b) assorting values from 8.78 to 552.97 M-1. The preferred solubilization of the chalcones in the micellar phase has been inferred.

Molecular organization and dynamics of micellar phase of polyelectrolyte-surfactant complexes: ESR spin probe study

NASA Astrophysics Data System (ADS)

Wasserman, A. M.; Kasaikin, V. A.; Zakharova, Yu. A.; Aliev, I. I.; Baranovsky, V. Yu.; Doseva, V.; Yasina, L. L.

2002-04-01

Molecular dynamics and organization of the micellar phase of complexes of linear polyelectrolytes with ionogenic and non-ionogenic surfactants was studied by the ESR spin probe method. Complexes of polyacrylic acid (PAA) and sodium polystyrenesulfonate (PSS) with alkyltrimethylammonium bromides (ATAB), as well as complexes of poly- N, N'-dimethyldiallylammonium chloride (PDACL) with sodium dodecylsulfate (SDS) were studied. The micellar phase of such complexes is highly organized molecular system, molecular ordering of which near the polymeric chain is much higher than in the 'center' of the micelle, it depends on the polymer-detergent interaction, flexibility of polymeric chain and length of carbonic part of the detergent molecule. Complexes of polymethacrylic acid (PMAA) with non-ionic detergent (dodecyl-substituted polyethyleneglycol), show that the local mobility of surfactant in such complexes is significantly lower than in 'free' micelles and depends on the number of micellar particles participating in formation of complexes.

Use of water-external micellar dispersions in oil recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.

1970-04-14

A water-external micellar dispersion followed by a mobility buffer and a water drive were used for enhanced oil recovery. Field Berea sandstone cores (19.6 percent porosity, 387 md permeability) were saturated with brine (16,500 ppM sodium chloride), flooded with crude oil from the Henry lease in Illinois (viscosity of 5.9 cp at 72/sup 0/F, specific gravity of 0.833), and waterflooded with water from Henry lease (17,210 ppM TDS). The micellar dispersion followed by the mobility buffer produced 99.6 percent of the oil in the core. The micellar slug contained ammonium petroleum sulfonate (MW 450), Henry crude oil, isopropanol, nonyl phenol,more » sodium hydroxide, and water from the Palestine water reservoir in Palestine, Illinois (412 ppM TDS). No. 530 Pusher, ammonium thiocyanate, isopropanol, and Palestine water were in the mobility buffer.« less

Micellar Drug Delivery and Proteomics Analysis for Effective Treatment of Resistant Prostate Cancer

DTIC Science & Technology

2015-12-01

22.4 g, 0.1 mol) dissolved in pyridine (50 mL) and CH2Cl2 (200 mL), and chilled to −78°C over dry ice. A solution of triphosgene (50 mmol, 14.8 g...chloroform, and precipitate in large amount of isopropanol and diethyl ether, followed by drying under vacuum for 48 h. Purified copolymer (100 mg...immunoassay. Biosens. Bioelectron. 2013, 39 (1), 296−9. (146) Shields, N.; Dodd, K. J.; Abblitt, C. Do children with Down Syndrome perform sufficient

Bacteriophage enzymes for the prevention and treatment of bacterial infections: Stability and stabilization of the enzyme lysing Streptococcus pyogenes cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klyachko, N. L.; Dmitrieva, N. F.; Eshchina, A. S.

2008-06-01

Recombinant, phage associated lytic enzyme Ply C capable to lyse streptococci of groups A and C was stabilized in the variety of the micelles containing compositions to improve the stability of the enzyme for further application in medicine. It was shown that, in the micellar polyelectrolyte composition M16, the enzyme retained its activity for 2 months; while in a buffer solution under the same conditions ((pH 6.3, room temperature), it completely lost its activity in 2 days

Effect of fractionation on treatment outcome in local dual-frequency sonication and Dox-encapsulated nanomicelles.

PubMed

Hasanzadeh, Hadi; Mokhtari-Dizaji, Manijhe; Bathaie, S Zahra; Hassan, Zuhair M

2013-10-01

The goal of this study was to localize drug release from nanomicelles using dual-frequency sonication at low levels of acoustic intensity. In this study, the antitumor effect of simultaneous dual-frequency sonication (28 kHz and 3 MHz) at low levels of acoustic intensity in combination with doxorubicin and micellar doxorubicin injection was assessed in a spontaneous model of breast adenocarcinoma in female Balb/c mice. Sixty-three tumor-bearing mice were randomly grouped into control, sham, dual-frequency sonication, doxorubicin injection with and without dual-frequency sonication, and micellar doxorubicin injection with and without dual-frequency sonication groups. The results of volume change relative to initial volume showed that in the micellar doxorubicin injection with sonication group, this parameter was significantly different from that of the control, sham, sonication, and doxorubicin injection groups (P < 0.05). In addition, the volume began to increase on the 15th day after the start of treatment, which is a good indication to repeat treatment; therefore, another group received an extra treatment on day 15. The animal life span in the micellar doxorubicin with sonication and repeated treatment groups was significantly higher than that in all the other experimental groups except for the micellar doxorubicin injection group (P < 0.05). It was concluded that dual-frequency sonication with micellar doxorubicin injection extends the life span relative to doxorubicin injection or dual-frequency sonication alone, and that repeating this treatment on day 15 decreases the rate of tumor growth significantly.

MICELLAR ELECTROKINETIC CHROMATOGRAPHY-MASS SPECTROMETRY (R823292)

EPA Science Inventory

The combination of micellar electrokinetic chromatography (MEKC) with mass spectrometry (MS) is very attractive for the direct identification of analyte molecules, for the possibility of selectivity enhancement, and for the structure confirmation and analysis in a MS-MS mode. The...

Temperature-dependent micellar structures in poly(styrene-b-isoprene) diblock copolymer solutions near the critical micelle temperature

NASA Astrophysics Data System (ADS)

Bang, Joona; Viswanathan, Karthik; Lodge, Timothy P.; Park, Moon Jeong; Char, Kookheon

2004-12-01

The temperature dependence of the micelle structures formed by poly(styrene-b-isoprene) (SI) diblock copolymers in the selective solvents diethyl phthalate (DEP) and tetradecane (C14), which are selective for the PS and PI blocks, respectively, have been investigated by small angle neutron scattering (SANS). Two nearly symmetric SI diblock copolymers, one with a perdeuterated PS block and the other with a perdeuterated PI block, were examined in both DEP and C14. The SANS scattering length density of the solvent was matched closely to either the core or the corona block. The resulting core and corona contrast data were fitted with a detailed model developed by Pedersen and co-workers. The fits provide quantitative information on micellar characteristics such as aggregation number, core size, overall size, solvent fraction in the core, and corona thickness. As temperature increases, the solvent selectivity decreases, leading to substantial solvent swelling of the core and a decrease in the aggregation number and core size. Both core and corona chains are able to relax their conformations near the critical micelle temperature due to a decrease in the interfacial tension, even though the corona chains are always under good solvent conditions.

Thermo- and pH-Responsive Copolymers Bearing Cholic Acid and Oligo(ethylene glycol) Pendants: Self-Assembly and pH-Controlled Release.

PubMed

Jia, Yong-Guang; Zhu, X X

2015-11-11

A family of block and random copolymers of norbornene derivatives bearing cholic acid and oligo(ethylene glycol) pendants were prepared in the presence of Grubbs' catalyst. The phase transition temperature of the copolymers in aqueous solutions may be tuned by the variation of comonomer ratios and pH values. Both types of copolymers formed micellar nanostructures with a hydrophilic poly(ethylene glycol) shell and a hydrophobic core containing cholic acid residues. The micellar size increased gradually with increasing pH due to the deprotonation of the carboxylic acid groups. These micelles were capable of encapsulating hydrophobic compounds such as Nile Red (NR). A higher hydrophobicity/hydrophilicity ratio in both copolymers resulted in a higher loading capacity for NR. With similar molecular weights and monomer compositions, the block copolymers showed a higher loading capacity for NR than the random copolymers. The NR-loaded micelles exhibited a pH-triggered release behavior. At pH 7.4 within 96 h, the micelles formed by the block and random of copolymers released 56 and 97% NR, respectively. Therefore, these micelles may have promise for use as therapeutic nanocarriers in drug delivery systems.

Impact of cationic surfactant on the self-assembly of sodium caseinate.

PubMed

Vinceković, Marko; Curlin, Marija; Jurašin, Darija

2014-08-27

The impact of a cationic surfactant, dodecylammonium chloride (DDACl), on the self-assembly of sodium caseinate (SC) has been investigated by light scattering, zeta potential, and rheological measurements as well as by microscopy (transmission electron and confocal laser scanning microscopy). In SC dilute solutions concentration-dependent self-assembly proceeds through the formation of spherical associates and their aggregation into elongated structures composed of connected spheres. DDACl interacts with SC via its hydrophilic and hydrophobic groups, inducing changes in SC self-assembled structures. These changes strongly depend on the surfactant aggregation states (monomeric or micellar) as well as concentration ratio of both components, leading to the formation of soluble and insoluble complexes of nano- to microdimensions. DDACl monomers interact with SC self-assembled entities in a different way compared to their micelles. Surfactant monomers form soluble complexes (similar to surfactant mixed micelles) at lower SC concentration but insoluble gelatinous complexes at higher SC concentration. At surfactant micellar concentration soluble complexes with casein chains wrapped around surfactant micelles are formed. This study suggests that the use of proper cationic surfactant concentration will allow modification and control of structural changes of SC self-assembled entities.

Solubilization of polycyclic aromatic hydrocarbons in micellar nonionic surfactant solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edwards, D.A.; Luthy, R.G.; Liu, Zhongbao

1991-01-01

Experimental data are presented on the enhanced apparent solubilities of naphthalene, phenanthrene, and pyrene resulting from solubilization in aqueous solutions of four commercial, nonionic surfactants: an alkyl polyoxyethylene (POE) type, two octylphenol POE types, and a nonylphenol POE type. Apparent solubilities of the polycyclic aromatic hydrocarbon (PAH) compounds in surfactant solutions were determined by radiolabeled techniques. Solubilization of each PAH compound commenced at the surfactant critical micelle concentration and was proportional to the concentration of surfactant in micelle form. The partitioning of organic compounds between surfactant micelles and aqueous solution is characterized by a mole fraction micelle-phase/aqueous-phase partition coefficient, K{submore » m}. Values of log K{sub m} for PAH compounds in surfactant solutions of this study range from 4.57 to 6.53. Log K{sub m} appears to be a linear function of log K{sub ow} for a given surfactant solution. A knowledge of partitioning in aqueous surfactant systems is a prerequisite to understanding mechanisms affecting the behavior of hydrophobic organic compounds in soil-water systems in which surfactants play a role in contaminant remediation or facilitated transport.« less

Inhibition of citral degradation in an acidic aqueous environment by polyoxyethylene alkylether surfactants.

PubMed

Maswal, Masrat; Dar, Aijaz Ahmad

2013-06-15

Citral is a flavour component widely used in food and cosmetic industries, but is chemically unstable and degrades over time in aqueous solutions due to acid-catalysed and oxidative reactions leading to loss of desirable flavour. The present study reveals the effect of non-ionic micellar solutions of Brij30 and Brij35 on the extent of solubilisation and stabilisation of citral. The rate of chemical degradation of citral in acidic aqueous solutions was found to be highest, which was subsequently reduced significantly within these studied surfactant systems, suggesting protection of citral from an acidic environment once it is incorporated into the micelles. The work concludes that polyoxyethylene alkylether surfactants with lower HLB value, less dense hydrophilic corona and more hydrophobic core volume are efficient in solubilising and stabilising citral against an acidic environment. Copyright © 2012 Elsevier Ltd. All rights reserved.

Physicochemical properties of micelles of poly(styrene-b-[3-(methacryloylamino)propyl]trimethylammonium chloride-b-ethylene oxide) in aqueous solutions.

PubMed

Liu, Jingjing; Liu, Dian; Yokoyama, Yuuichi; Yusa, Shin-Ichi; Nakashima, Kenichi

2009-01-20

Polymeric micelles from a new triblock copolymer, polystyrene-block-poly[(3-(methacryloylamino)propyl)trimethylammonium chloride]-block-poly(ethylene oxide) (PS-b-PMAPTAC-b-PEO), were prepared in aqueous solutions and characterized by various techniques including dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence spectroscopy. The micelle consists of a PS core, PMAPTAC shell, and PEO corona. It was revealed by SEM and DLS measurements that the micelles have a spherical structure with a hydrodynamic diameter about 75 nm. The addition of tungstate to the micellar solution caused a morphological change in the micelles from extended to shrunken spheres, which can be attributed to the fact that electrostatic repulsion among the cationic PMAPTAC blocks is canceled by the negative charge of the bound tungstate ions. Effective incorporation of tungstate ions into the micelles were confirmed by TEM and zeta-potential measurements.

Paclitaxel solubility in aqueous dispersions and mixed micellar solutions of lecithin.

PubMed

Sznitowska, Malgorzata; Klunder, Malgorzata; Placzek, Marcin

2008-01-01

The aim of this study was to find a biocompatible, lecithin-based carrier for paclitaxel (PTX) suitable for intravenous infusion and ensuring a soluble PTX concentration of 100 mg/100 ml or higher for at least 24 h. Aqueous dispersions of egg or soya lecithin (water-lecithin dispersions, WLD), mixed micellar (MM) solutions of egg lecithin and sodium deoxycholate, and formulations containing lecithin plus the co-surfactants and co-solvents poloxamer, polysorbate, Span, benzalkonium chloride, and macrogol were investigated. Amorphous PTX was prepared by lyophilization. PTX co-lyophilized with surfactants was also studied. Unlike crystalline PTX, the drug in an amorphous form is easily soluble in 1-5% (w/w) WLD or in MM. The highest solubility (up to 570 mg/100 ml) was achieved in 5% WLD. Dissolved PTX precipitated from all tested formulations over 24 h. Despite this, concentrations of dissolved PTX of 100 mg/100 ml or higher were observed after 24 h in 5% egg WLD, 1-5% soya WLD, and in 5% MM (lecithin : deoxycholate ratio 1 : 1 w/w). When four different batches of 5% egg WLD were prepared, containing PTX in clinically relevant concentration of 100 mg/100 ml, no precipitation of PTX was observed within 24 h and this formulation is the most promising candidate for further in vivo studies. Neither additional surfactants nor co-lyophilization increased PTX solubility in the lecithin-based carriers. The use of parenteral emulsions as solvents for the co-lyophilized PTX also failed to increase the solubility of the drug up to the target concentration.

Influence of the hydrophilic head size and hydrophobic tail length of surfactants on the ability of micelles to stabilize citral.

PubMed

Hong, Chi Rac; Park, Sung Joon; Choi, Seung Jun

2016-07-01

Surfactant-made micelles can control the rate of chemical degradation of poorly water-soluble food flavors. To evaluate how the molecular structure of surfactant has an influence on the chemical decomposition rate of citral, micelles were prepared with polyoxyethylene alkyl ether-type surfactants that had similar molecular structures but various hydrophilic head sizes and hydrophobic tail lengths. At a critical 20× micelle concentration of surfactant, there was no significant difference in the chemical degradation rate of citral in micelles in neutral pH, regardless of the hydrophilic head size or hydrophobic tail length. In an acidic environment, the degradation rate constant of citral generally increased proportionally with increasing hydrophilic head size of surfactant (0.1563 and 0.2217 for surfactants with 23 and 100 oxyethylene units, respectively) but the length of hydrophobic tail did not affect the citral stability. Also, little difference (0.2217 and 0.2265 for surfactant having 100 oxyethylene units with and without Fe(3+) ) in degradation rate constant of citral between simple micellar solution and micellar solution containing iron suggested that iron ions could not accelerate citral degradation in micelles, regardless of the form of iron (Fe(2+) and Fe(3+) ). This work concludes that although the concentration of surfactant could be relevant, if its concentration could be controlled in the same manner as the critical micelle concentration, then a polyethylene alkyl ether-type surfactant with a small hydrophilic head could more efficiently stabilize citral at an acidic pH. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

The antimicrobial and antiadhesion activities of micellar solutions of surfactin, CTAB and CPCl with terpinen-4-ol: applications to control oral pathogens.

PubMed

Bucci, Andreia R; Marcelino, Larissa; Mendes, Renata K; Etchegaray, Augusto

2018-06-06

The oral pathogen Streptococcus mutans is involved in tooth decay by a process that initiates with biofilm adhesion and caries development. The presence of other microbes such as Candida albicans may worsen the demineralization process. Since both microbes are virulent to the host and will proliferate under specific host immune deficiencies and systemic diseases, it is important to study antimicrobial substances and their effects on both pathogens. There are several antiseptic agents used to reduce plaque biofilm and its outcome (dental caries and/or periodontal disease). However, some of these have undesired effects. In the current study we investigated the antimicrobial and anti-adhesion properties of micellar solutions of surfactants and the plant natural product terpinen-4-ol (TP). The results revealed an increase in antimicrobial properties of the synthetic surfactants, cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTAB), when mixed with TP. In addition, although surfactin, a biosurfactant, has little antimicrobial activity, it was demonstrated that it enhanced the effect of TP both as antimicrobial and anti-adhesion compound. Surfactin and the synthetic surfactants promote the antimicrobial activity of TP against S. mutans, the causal agent of tooth decay, suggesting specificity for membrane interactions that may be facilitated by surfactants. This is the first report on the successful use of surfactin in association with TP to inhibit the growth and adhesion of microbial pathogens. Surfactin has other beneficial properties besides being biodegradable, it has antiviral and anti-mycoplasma activities in addition to adjuvant properties and encapsulating capacity at low concentration.

Temperature-dependent magnetic field effect study on exciplex luminescence: probing the triton X-100 reverse micelle in cyclohexane.

PubMed

Das, Doyel; Nath, Deb Narayan

2007-09-20

The microenvironment within the reverse micelle of the nonionic surfactant Triton X-100 (TX-100) in cyclohexane has been investigated by studying the magnetic field effect (MFE) on pyrene-dimethylaniline exciplex luminescence. The nature of exciplex fluorescence and its behavior in the presence of a magnetic field have been found to vary significantly with the water content of the medium. Results are discussed in light of multiple exciplex formation within the micelle which is further supported by the fluorescence lifetime measurements. Those exciplexes emitting at longer wavelength are found to be magnetic field sensitive while those emitting toward the blue region of the spectrum are insensitive toward magnetic field. Since the exciplex's emission characteristics and magnetic field sensitivity depend on its immediate surrounding, it has been concluded that the environment within the micelle is nonuniform. With an increase in hydration level, different zones of varying polarity are created within the reverse micelle. It has been pointed out that the magnetic field sensitive components reside inside the polar core of the micelle while those located near the hydrocarbon tail are field insensitive. However it has been presumed that an interconversion between the different types of exciplexes is possible. The environment within the reverse micelle is found to be largely affected by the change in temperature, and this is reflected in the exciplex emission property and the extent of magnetic field effect. Interestingly, the variation of MFE with temperature follows different trends in the dry and the wet reverse micelle. A comparison has been drawn with the reverse micelle of the ionic surfactant to get an insight into the difference between the various types of micellar environment.

Surface Attachment of Gold Nanoparticles Guided by Block Copolymer Micellar Films and Its Application in Silicon Etching

PubMed Central

Wei, Mingjie; Wang, Yong

2015-01-01

Patterning metallic nanoparticles on substrate surfaces is important in a number of applications. However, it remains challenging to fabricate such patterned nanoparticles with easily controlled structural parameters, including particle sizes and densities, from simple methods. We report on a new route to directly pattern pre-formed gold nanoparticles with different diameters on block copolymer micellar monolayers coated on silicon substrates. Due to the synergetic effect of complexation and electrostatic interactions between the micellar cores and the gold particles, incubating the copolymer-coated silicon in a gold nanoparticles suspension leads to a monolayer of gold particles attached on the coated silicon. The intermediate micellar film was then removed using oxygen plasma treatment, allowing the direct contact of the gold particles with the Si substrate. We further demonstrate that the gold nanoparticles can serve as catalysts for the localized etching of the silicon substrate, resulting in nanoporous Si with a top layer of straight pores. PMID:28793407

Micellar modification of drug stability: analysis of the effect of hexadecyltrimethylammonium halides on the rate of degradation of cephaclor.

PubMed

Oliveira, A G; Cuccovia, I M; Chaimovich, H

1990-01-01

The intra- and intermolecular rates of degradation of cephaclor were determined with and without hexadecyltrimethylammonium bromide (CTABr). Micellar-derived spectral shifts were used to measure the association of the ionic forms as well as to determine the effect of CTABr on the apparent acid dissociation constant of the antibiotic. The rate of degradation of cephaclor increased with detergent and was salt sensitive. Micellar effects were analyzed quantitatively within the framework of the pseudophase ion exchange model. All experimental data were fitted to this model which was used to predict the combined effects of pH and detergent concentration. Micelles increased the rate of OH- attack on cephaclor; most of the effect was due to the concentration of reagents in the micellar pseudophase. The intramolecular degradation was catalyzed 25-fold by micelles, and a working hypothesis to rationalize this effect is proposed. The results demonstrate that quantitative analysis can be utilized to assess and predict effects of detergents on drug stability.

Synthesis and antibacterial activity of water-dispersible silver nanoparticles via micellar nanoreactors

NASA Astrophysics Data System (ADS)

Pofali, Prasad; Shirolikar, Seema; Borde, Lalit; Pattani, Aditya; Dandekar, Prajakta; Jain, Ratnesh

2018-04-01

We have synthesized silver nanoparticles (AgNPs) using micelles of sugar fatty acid ester by dissolving the surfactant in a mixture of iso-octane and n-butanol, with solid-liquid extraction. Highly concentrated, water-dispersible AgNPs were obtained after thorough washing with alcohol, to remove excess of sucrose fatty acid ester DK SS and salt, followed by drying. The particles were characterized for their size, morphology and crystallinity using UV-Visible spectrophotometry, Transmission Electron Microscopy and x-ray diffractometry. Antibacterial study, confirmed the activity of nanoparticles against E. coli, P. aeruginosa and S. aureus, which causes diseases including diarrhoea and several life-threatening infections. Antibacterial activity of E. coli and P. aeruginosa was found to be 2.5 fold and for S. aureus 1.6 fold compared to 50 ppm conc. of Silver Nitrate. Our method of producing nanoparticles is employed as a platform technology for synthesizing other inorganic nanoparticles. This is the first report discussing the use of micellar carriers for obtaining silver nanopowder, to the best of our knowledge, which has the potential to overcome limitations during fabrication of AgNPs using reverse/inverse micelles. Our method yielded nano-sized, water-dispersible AgNPs via an easy and economic approach. The one-pot approach possesses advantages in terms of cost and simplicity, as compared with traditional methods of producing powdered AgNPs using energy intensive and expensive techniques like lyophilisation. The developed method, thus, possesses immense potential for commercial synthesis of AgNPs.

Medium-dependent interactions of quinones with cytosine and cytidine: a laser flash photolysis study with magnetic field effect.

PubMed

Bose, Adity; Basu, Samita

2009-03-01

Laser flash photolysis and an external magnetic field have been used for the study of the interaction of two quinone molecules, namely, 9,10-anthraquinone (AQ) and 2-methyl 1,4-naphthoquinone (or menadione, MQ) with a DNA base, cytosine (C) and its nucleoside cytidine (dC) in two media, a homogeneous one composed of acetonitrile/water (ACN/H(2)O, 9:1, v/v) and a SDS micellar heterogeneous one. We have applied an external magnetic field for the proper identification of the transients formed during the interactions in micellar media. Cytosine exhibits electron transfer (ET) followed by hydrogen abstraction (HA) while dC reveals a reduced ET compared to C, with both quinones in organic homogeneous medium (ACN/H(2)O). Due to a higher electron affinity, AQ supports more faciler ET than MQ with dC in ACN/H(2)O but observations in SDS have been just the reverse. In SDS, ET from dC is completely quenched and a dominant HA is all that could be discerned. This work reveals two main findings: first, a drop in ET on addition of a ribose unit to C, which has been attributed to a role of keto-enol tautomerism in inducing ET from electron-rich nucleus and second, the effect of medium in controlling reaction mechanism by favoring HA with AQ although it is intrinsically more prone towards ET.

Surfactant enhanced remediation of soil columns contaminated by residual tetrachloroethylene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pennell, K.D.; Jin, M.; Abriola, L.M.

1994-01-01

The ability of aqueous surfactant solutions to recover tetrachloroethylene (PCE) entrapped in Ottawa sand was evaluated in four column experiments. Residual PCE was emplaced by injecting (14)C-labeled PCE into water-saturated soil columns and displacing the free product with water. Miscible displacement experiments were conducted before and after PCE entrapment to determine the influence or residual PCE on column dispersivities. The first two column studies involved the injection of a 4% solution of polyoxyethylene (POE) (20) sorbitan monooleate, resulting in the removal of 90% and 97% of the residual PCE from 20-30- and 40-120-mesh Ottawa sand, respectively. Although micellar solubilization ofmore » PCE was the primary mode of recovery in these experiments, this process was shown to be rate-limited.« less

PEGylated polylysine dendrimers increase lymphatic exposure to doxorubicin when compared to PEGylated liposomal and solution formulations of doxorubicin.

PubMed

Ryan, Gemma M; Kaminskas, Lisa M; Bulitta, Jürgen B; McIntosh, Michelle P; Owen, David J; Porter, Christopher J H

2013-11-28

Improved delivery of chemotherapeutic drugs to the lymphatic system has the potential to augment outcomes for cancer therapy by enhancing activity against lymph node metastases. Uptake of small molecule chemotherapeutics into the lymphatic system, however, is limited. Nano-sized drug carriers have the potential to promote access to the lymphatics, but to this point, this has not been examined in detail. The current study therefore evaluated the lymphatic exposure of doxorubicin after subcutaneous and intravenous administration as a simple solution formulation or when formulated as a doxorubicin loaded PEGylated poly-lysine dendrimer (hydrodynamic diameter 12 nm), a PEGylated liposome (100 nm) and various pluronic micellar formulations (~5 nm) to thoracic lymph duct cannulated rats. Plasma and lymph pharmacokinetics were analysed by compartmental pharmacokinetic modelling in S-ADAPT, and Berkeley Madonna software was used to predict the lymphatic exposure of doxorubicin over an extended period of time. The micelle formulations displayed poor in vivo stability, resulting in doxorubicin profiles that were similar to that observed after administration of the doxorubicin solution formulation. In contrast, the dendrimer formulation significantly increased the recovery of doxorubicin in the thoracic lymph after both intravenous and subcutaneous dosing when compared to the solution or micellar formulation. Dendrimer-doxorubicin also resulted in increases in lymphatic doxorubicin concentrations when compared to the liposome formulation, although liposomal doxorubicin did increase lymphatic transport when compared to the solution formulation. Specifically, the dendrimer formulation increased the recovery of doxorubicin in the lymph up to 30 h post dose by up to 685 fold and 3.7 fold when compared to the solution and liposomal formulations respectively. Using the compartmental model to predict lymphatic exposure to longer time periods suggested that doxorubicin exposure to the lymphatic system would ultimately be 9796 times and 6.1 times greater after administration of dendrimer doxorubicin when compared to the solution and liposome formulations respectively. The recovery of doxorubicin in the sentinel lymph nodes draining the subcutaneous injection site was also quantified directly, and consistent with the lymph pharmacokinetic data, lymph node recovery was greatest for the dendrimer formulation (12% of dosed doxorubicin/g node) when compared to the liposome (1.4%/g node) and solution (<1%/g node) formulations. The data suggest that dendrimer-based drug delivery systems have the potential to enhance drug exposure to lymph-based drug targets such as lymphatic metastases. © 2013.

TRACE ANALYSIS OF FLUORESCEIN-DERIVATIZED PHENOXY ACID HERBICIDES BY MICELLAR ELECTROKINETIC CHROMATOGRAPHY WITH LASER-INDUCTED FLUORESCENCE DETECTION

EPA Science Inventory

Micellar electrokinetic chromatography (MEKC) with laser-induced fluorescence (LIF) detection was used for the trace analysis of phenoxy acid herbicides. Capillary electrophoresis (CE) with LIF detection, which has not previously been used for pesticide analysis, overcomes the po...

Formation of DNA Adducts by Ellipticine and Its Micellar Form in Rats — A Comparative Study

PubMed Central

Stiborova, Marie; Manhartova, Zuzana; Hodek, Petr; Adam, Vojtech; Kizek, Rene; Frei, Eva

2014-01-01

The requirements for early diagnostics as well as effective treatment of cancer diseases have increased the pressure on development of efficient methods for targeted drug delivery as well as imaging of the treatment success. One of the most recent approaches covering the drug delivery aspects is benefitting from the unique properties of nanomaterials. Ellipticine and its derivatives are efficient anticancer compounds that function through multiple mechanisms. Formation of covalent DNA adducts after ellipticine enzymatic activation is one of the most important mechanisms of its pharmacological action. In this study, we investigated whether ellipticine might be released from its micellar (encapsulated) form to generate covalent adducts analogous to those formed by free ellipticine. The 32P-postlabeling technique was used as a useful imaging method to detect and quantify covalent ellipticine-derived DNA adducts. We compared the efficiencies of free ellipticine and its micellar form (the poly(ethylene oxide)-block-poly(allyl glycidyl ether) (PAGE-PEO) block copolymer, P 119 nanoparticles) to form ellipticine-DNA adducts in rats in vivo. Here, we demonstrate for the first time that treatment of rats with ellipticine in micelles resulted in formation of ellipticine-derived DNA adducts in vivo and suggest that a gradual release of ellipticine from its micellar form might produce the enhanced permeation and retention effect of this ellipticine-micellar delivery system. PMID:25479328

Formation of DNA adducts by ellipticine and its micellar form in rats - a comparative study.

PubMed

Stiborova, Marie; Manhartova, Zuzana; Hodek, Petr; Adam, Vojtech; Kizek, Rene; Frei, Eva

2014-12-03

The requirements for early diagnostics as well as effective treatment of cancer diseases have increased the pressure on development of efficient methods for targeted drug delivery as well as imaging of the treatment success. One of the most recent approaches covering the drug delivery aspects is benefitting from the unique properties of nanomaterials. Ellipticine and its derivatives are efficient anticancer compounds that function through multiple mechanisms. Formation of covalent DNA adducts after ellipticine enzymatic activation is one of the most important mechanisms of its pharmacological action. In this study, we investigated whether ellipticine might be released from its micellar (encapsulated) form to generate covalent adducts analogous to those formed by free ellipticine. The (32)P-postlabeling technique was used as a useful imaging method to detect and quantify covalent ellipticine-derived DNA adducts. We compared the efficiencies of free ellipticine and its micellar form (the poly(ethylene oxide)-block-poly(allyl glycidyl ether) (PAGE-PEO) block copolymer, P 119 nanoparticles) to form ellipticine-DNA adducts in rats in vivo. Here, we demonstrate for the first time that treatment of rats with ellipticine in micelles resulted in formation of ellipticine-derived DNA adducts in vivo and suggest that a gradual release of ellipticine from its micellar form might produce the enhanced permeation and retention effect of this ellipticine-micellar delivery system.

Re-appearance of cooperativity in ultra-small spin-crossover [Fe(pz){Ni(CN)₄}] nanoparticles.

PubMed

Peng, Haonan; Tricard, Simon; Félix, Gautier; Molnár, Gábor; Nicolazzi, William; Salmon, Lionel; Bousseksou, Azzedine

2014-10-06

A reverse nanoemulsion technique was used for the elaboration of [Fe(pz){Ni(CN)4}] nanoparticles. Low-temperature micellar exchange made it possible to elaborate ultra-small nanoparticles with sizes down to 2 nm. When decreasing the size of the particles from 110 to 12 nm the spin transition shifts to lower temperatures, becomes gradual, and the hysteresis shrinks. On the other hand, a re-opening of the hysteresis was observed for smaller (2 nm) particles. A detailed (57)Fe Mössbauer spectroscopy analysis was used to correlate this unusual phenomenon to the modification of the stiffness of the nanoparticles thanks to the determination of their Debye temperature. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Cerium(III) and ionic liquids on the clouding behavior of Triton X-100 micelles

NASA Astrophysics Data System (ADS)

Sen, Indrani Das; Negi, Charu; Jayaram, Radha V.

2018-04-01

In the present study, the effect of Ce(III) on the clouding behavior of Triton X-100 has been investigated in the presence and absence of imidazolium based ionic liquids of varying chain length and counter ions. Thermodynamic parameters of clouding were calculated to comprehend the underlying interactions between the surfactant and the additives. The cloud point (CP) of Triton X-100 was found to increase with the concentration of Ce(III) and that of the ionic liquids studied. This increase of CP reflects the solubilization of the ionic liquids in the micellar solution1.

Self-assembled micellar nanocomplexes comprising green tea catechin derivatives and protein drugs for cancer therapy

NASA Astrophysics Data System (ADS)

Chung, Joo Eun; Tan, Susi; Gao, Shu Jun; Yongvongsoontorn, Nunnarpas; Kim, Soon Hee; Lee, Jeong Heon; Choi, Hak Soo; Yano, Hirohisa; Zhuo, Lang; Kurisawa, Motoichi; Ying, Jackie Y.

2014-11-01

When designing drug carriers, the drug-to-carrier ratio is an important consideration, because the use of high quantities of carriers can result in toxicity as a consequence of poor metabolism and elimination of the carriers. However, these issues would be of less concern if both the drug and carrier had therapeutic effects. (-)-Epigallocatechin-3-O-gallate (EGCG), a major ingredient of green tea, has been shown, for example, to possess anticancer effects, anti-HIV effects, neuroprotective effects and DNA-protective effects. Here, we show that sequential self-assembly of the EGCG derivative with anticancer proteins leads to the formation of stable micellar nanocomplexes, which have greater anticancer effects in vitro and in vivo than the free protein. The micellar nanocomplex is obtained by complexation of oligomerized EGCG with the anticancer protein Herceptin to form the core, followed by complexation of poly(ethylene glycol)-EGCG to form the shell. When injected into mice, the Herceptin-loaded micellar nanocomplex demonstrates better tumour selectivity and growth reduction, as well as longer blood half-life, than free Herceptin.

Quantitative analysis of flavonoids and phenolic acids in Arnica montana L. by micellar electrokinetic capillary chromatography.

PubMed

Ganzera, Markus; Egger, Christoph; Zidorn, Christian; Stuppner, Hermann

2008-05-05

Arnica montana preparations have been used in Europe for centuries to treat skin disorders. Among the biologically active ingredients in the flower heads of the plant are sequiterpenes, flavonoids and phenolic acids. For the simultaneous determination of compounds belonging to the latter two groups a micellar electrokinetic capillary chromatography (MEKC) method was developed and validated. By using an electrolyte solution containing 50 mM borax, 25 mM sodium dodecyl sulfate and 30% of acetonitrile the separation of seven flavonoids and four caffeic acid derivatives was feasible in less than 20 min. The optimized system was validated for repeatability (sigma(rel) < or = 4.4%), precision (inter-day sigma(rel) < or = 8.13%, intra-day sigma(rel) < or = 4.32%), accuracy (recovery rates from 96.8 to 102.4%), sensitivity (limit of detection (LOD) < or = 4.5 microg mL(-1)) and linearity (R(2) > or = 0.9996), and then successfully applied to assay several plant samples. In all of them the most dominant flavonoid was found to be quercetin 3-O-glucuronic acid, whereas 3,5-dicaffeoylquinic acid was the major phenolic acid; the total content of flavonoids and phenolic acids varied in the samples from 0.60 to 1.70%, and 1.03 to 2.24%, respectively.

Monitoring the quality consistency of Fufang Danshen Pills using micellar electrokinetic chromatography fingerprint coupled with prediction of antioxidant activity and chemometrics.

PubMed

Ji, Zhengchao; Sun, Wanyang; Sun, Guoxiang; Zhang, Jin

2016-08-01

A fast micellar electrokinetic chromatography fingerprint method combined with quantification was developed and validated to evaluate the quality of Fufang Danshen Pills, a traditional Chinese Medicine, which has been used in the treatment of cardiovascular system diseases, in which the tetrahedron optimization method was first used to optimize the background electrolyte solution. Subsequently, the index of the fingerprint information amount of I was performed as an excellent objective indictor to investigate the experimental conditions. In addition, a systematical quantified fingerprint method was constructed for evaluating the quality consistency of 20 batches of test samples obtained from the same drug manufacturer. The fingerprint analysis combined with quantitative determination of two components showed that the quality consistency of the test samples was quite good within the same commercial brand. Furthermore, the partial least squares model analysis was used to explore the fingerprint-efficacy relationship between active components and antioxidant activity in vitro, which can be applied for the assessment of anti-oxidant activity of Fufang Danshen pills and provide valuable medicinal information for quality control. The result illustrated that the present study provided a reliable and reasonable method for monitoring the quality consistency of Fufang Danshen pills. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stabilized micelles as delivery vehicles for paclitaxel.

PubMed

Yoncheva, Krassimira; Calleja, Patricia; Agüeros, Maite; Petrov, Petar; Miladinova, Ivanka; Tsvetanov, Christo; Irache, Juan M

2012-10-15

Paclitaxel is an antineoplastic drug used against a variety of tumors, but its low aqueous solubility and active removal caused by P-glycoprotein in the intestinal cells hinder its oral administration. In our study, new type of stabilized Pluronic micelles were developed and evaluated as carriers for paclitaxel delivery via oral or intravenous route. The pre-stabilized micelles were loaded with paclitaxel by simple solvent/evaporation technique achieving high encapsulation efficiency of approximately 70%. Gastrointestinal transit of the developed micelles was evaluated by oral administration of rhodamine-labeled micelles in rats. Our results showed prolonged gastrointestinal residence of the marker encapsulated into micelles, compared to a solution containing free marker. Further, the oral administration of micelles in mice showed high area under curve of micellar paclitaxel (similar to the area of i.v. Taxol(®)), longer mean residence time (9-times longer than i.v. Taxol(®)) and high distribution volume (2-fold higher than i.v. Taxol(®)) indicating an efficient oral absorption of paclitaxel delivered by micelles. Intravenous administration of micelles also showed a significant improvement of pharmacokinetic parameters of micellar paclitaxel vs. Taxol(®), in particular higher area under curve (1.2-fold), 5-times longer mean residence time and lower clearance, indicating longer systemic circulation of the micelles. Copyright © 2012 Elsevier B.V. All rights reserved.

Interaction of Huntingtin Exon-1 Peptides with Lipid-Based Micellar Nanoparticles Probed by Solution NMR and Q-Band Pulsed EPR.

PubMed

Ceccon, Alberto; Schmidt, Thomas; Tugarinov, Vitali; Kotler, Samuel A; Schwieters, Charles D; Clore, G Marius

2018-05-23

Lipid-based micellar nanoparticles promote aggregation of huntingtin exon-1 peptides. Here we characterize the interaction of two such peptides, htt NT Q  7 and htt NT Q  10 comprising the N-terminal amphiphilic domain of huntingtin followed by 7 and 10 glutamine repeats, respectively, with 8 nm lipid micelles using NMR chemical exchange saturation transfer (CEST), circular dichroism and pulsed Q-band EPR. Exchange between free and micelle-bound htt NT Q  n peptides occurs on the millisecond time scale with a K D ∼ 0.5-1 mM. Upon binding micelles, residues 1-15 adopt a helical conformation. Oxidation of Met 7 to a sulfoxide reduces the binding affinity for micelles ∼3-4-fold and increases the length of the helix by a further two residues. A structure of the bound monomer unit is calculated from the backbone chemical shifts of the micelle-bound state obtained from CEST. Pulsed Q-band EPR shows that a monomer-dimer equilibrium exists on the surface of the micelles and that the two helices of the dimer adopt a parallel orientation, thereby bringing two disordered polyQ tails into close proximity which may promote aggregation upon dissociation from the micelle surface.

Rapid determination of piracetam in human plasma and cerebrospinal fluid by micellar electrokinetic chromatography with sample direct injection.

PubMed

Yeh, Hsin-Hua; Yang, Yuan-Han; Ko, Ju-Yun; Chen, Su-Hwei

2006-07-07

A simple micellar electrokinetic chromatography (MEKC) method with UV detection at 200 nm for analysis of piracetam in plasma and in cerebrospinal fluid (CSF) by direct injection without any sample pretreatment is described. The separation of piracetam from biological matrix was performed at 25 degrees C using a background electrolyte consisting of Tris buffer with sodium dodecyl sulfate (SDS) as the electrolyte solution. Several parameters affecting the separation of the drug from biological matrix were studied, including the pH and concentrations of the Tris buffer and SDS. Under optimal MEKC condition, good separation with high efficiency and short analyses time is achieved. Using imidazole as an internal standard (IS), the linear ranges of the method for the determination of piracetam in plasma and in CSF were all between 5 and 500 microg/mL; the detection limit of the drug in plasma and in CSF (signal-to-noise ratio=3; injection 0.5 psi, 5s) was 1.0 microg/mL. The applicability of the proposed method for determination of piracetam in plasma and CSF collected after intravenous administration of 3g piracetam every 6h and oral administration 1.2g every 6h in encephalopathy patients with aphasia was demonstrated.

Application of saponin biosurfactant and its recovery in the MEUF process for removal of methyl violet from wastewater.

PubMed

Samal, Kulbhushan; Das, Chandan; Mohanty, Kaustubha

2017-12-01

The potential of saponin, a biosurfactant, in the micellar enhanced ultrafiltration (MEUF) process was tested systematically for removal of methyl violet from wastewater. For this, the aqueous extract of reetha (Sapindus mukorossi) pericarp which contains saponin was used as the biosurfactant. First, the micellar solubilization of methyl violet in saponin micelles was investigated in terms of molar solubilization power (SP) of saponin. It was observed that the adsorption of methyl violet on the agglomerates of saponin micelles was mainly responsible for the enhanced solubilization. The Gibbs free energy of solubilization (calculated as -29.63 kJ mol -1 ) suggested that process was feasible and spontaneous. The MEUF experiments were performed in batch as well as continuous mode using saponin biosurfactant, and the effect of operating parameters on permeate flux and solute retention were evaluated. The removal of methyl violet in MEUF process was >99% achieved with 10 kDa polyethersulfone (PES) membrane for feed dye concentration of 250 mg L -1 at studied conditions. Finally, the saponin in permeate was recovered using n-heptane and n-butanol by solvent extraction process. The solvent n-butanol showed better extraction efficiency as compared to n-heptane for saponin extraction. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechano-responsive hydrogels crosslinked by reactive block copolymer micelles

NASA Astrophysics Data System (ADS)

Xiao, Longxi

Hydrogels are crosslinked polymeric networks that can swell in water without dissolution. Owing to their structural similarity to the native extracelluar matrices, hydrogels have been widely used in biomedical applications. Synthetic hydrogels have been designed to respond to various stimuli, but mechanical signals have not incorporated into hydrogel matrices. Because most tissues in the body are subjected to various types of mechanical forces, and cells within these tissues have sophisticated mechano-transduction machinery, this thesis is focused on developing hydrogel materials with built-in mechano-sensing mechanisms for use as tissue engineering scaffolds or drug release devices. Self-assembled block copolymer micelles (BCMs) with reactive handles were employed as the nanoscopic crosslinkers for the construction of covalently crosslinked networks. BCMs were assembled from amphiphilic diblock copolymers of poly(n-butyl acrylate) and poly(acrylic acid) partially modified with acrylate. Radical polymerization of acrylamide in the presence of micellar crosslinkers gave rise to elastomeric hydrogels whose mechanical properties can be tuned by varying the BCM composition and concentration. TEM imaging revealed that the covalently integrated BCMs underwent strain-dependent reversible deformation. A model hydrophobic drug, pyrene, loaded into the core of BCMs prior to the hydrogel formation, was dynamically released in response to externally applied mechanical forces, through force-induced reversible micelle deformation and the penetration of water molecules into the micelle core. The mechano-responsive hydrogel has been studied for tissue repair and regeneration purposes. Glycidyl methacrylate (GMA)-modified hyaluronic acid (HA) was photochemically crosslinked in the presence of dexamethasone (DEX)-loaded crosslinkable BCMs. The resultant HA gels (HAxBCM) contain covalently integrated micellar compartments with DEX being sequestered in the hydrophobic core. Compared to the traditional HA gels prepared by radical crosslinking of HAGMA, HAxBCM gels exhibited improved drug loading and release capacity. Moreover, compressive forces exerted on the gels were transmitted to the crosslinked BCMs, resulting in a force-modulated DEX release on demand. Micelle mobility in the crosslinked networks was analyzed by fluorescence correlation spectroscopy using nile red loaded BCMs. The anti-inflammatory activities of DEX-releasing HAxBCM gels were evaluated via the in vitro culture of lipopolysaccharide-activated macrophages.

An Investigation of Aggregation in Synergistic Solvent Extraction Systems

NASA Astrophysics Data System (ADS)

Jackson, Andy Steven

With an increasing focus on anthropogenic climate change, nuclear reactors present an attractive option for base load power generation with regard to air pollution and carbon emissions, especially when compared with traditional fossil fuel based options. However, used nuclear fuel (UNF) is highly radiotoxic and contains minor actinides (americium and curium) which remain more radiotoxic than natural uranium ore for hundreds of thousands of years, presenting a challenge for long-term storage . Advanced nuclear fuel recycling can reduce this required storage time to thousands of years by removing the highly radiotoxic minor actinides. Many advanced separation schemes have been proposed to achieve this separation but none have been implemented to date. A key feature among many proposed schemes is the use of more than one extraction reagent in a single extraction phase, which can lead to the phenomenon known as "synergism" in which the extraction efficiency for a combination of the reagents is greater than that of the individual extractants alone. This feature is not well understood for many systems and a comprehensive picture of the mechanism behind synergism does not exist. There are several proposed mechanisms for synergism though none have been used to model multiple extraction systems. This work examines several proposed advanced extractant combinations which exhibit synergism: 2-bromodecanoic acid (BDA) with 2,2':6',2"-terpyridine (TERPY), tri-n-butylphosphine oxide (TPBO) with 2-thenoyltrifluoro acetone (HTTA), and dinonylnaphthalene sulfonic acid (HDNNS) with 5,8-diethyl-7-hydroxy-dodecan-6-oxime (LIX). We examine two proposed synergistic mechanisms involving and attempt to verify the ability of these mechanisms to predict the extraction behavior of the chosen systems. These are a reverse micellar catalyzed extraction model and a mixed complex formation model. Neither was able to effectively predict the synergistic behavior of the systems. We further examine these systems for the presence of large reverse micellar aggregates and thermodynamic signatures of aggregation. Behaviors differed widely from system to system, suggesting the possibility of more than one mechanism being responsible for similar observed extraction trends.

NMR structures in different membrane environments of three ocellatin peptides isolated from Leptodactylus labyrinthicus.

PubMed

Gomes, Karla A G G; Dos Santos, Daniel M; Santos, Virgílio M; Piló-Veloso, Dorila; Mundim, Higor M; Rodrigues, Leticia V; Lião, Luciano M; Verly, Rodrigo M; de Lima, Maria Elena; Resende, Jarbas M

2018-05-01

The peptides ocellatin-LB1, -LB2 and -F1 have previously been isolated from anurans of the Leptodactylus genus and the sequences are identical from residue 1-22, which correspond to ocellatin-LB1 sequence (GVVDILKGAAKDIAGHLASKVM-NH 2 ), whereas ocellatin-LB2 carries an extra N and ocellatin-F1 extra NKL residues at their C-termini. These peptides showed different spectra of activities and biophysical investigations indicated a direct correlation between membrane-disruptive properties and antimicrobial activities, i.e. ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. To better characterize their membrane interactions, we report here the detailed three-dimensional NMR structures of these peptides in TFE-d 2 :H 2 O (60:40) and in the presence of zwitterionic DPC-d 38 and anionic SDS-d 25 micellar solutions. Although the three peptides showed significant helical contents in the three mimetic environments, structural differences were noticed. When the structures of the three peptides in the presence of DPC-d 38 micelles are compared to each other, a more pronounced curvature is observed for ocellatin-F1 and the bent helix, with the concave face composed mostly of hydrophobic residues, is consistent with the micellar curvature and the amphipathic nature of the molecule. Interestingly, an almost linear helical segment was observed for ocellatin-F1 in the presence of SDS-d 25 micelles and the conformational differences in the two micellar environments are possibly related to the presence of the extra Lys residue near the peptide C-terminus, which increases the affinity of ocellatin-F1 to anionic membranes in comparison with ocellatin-LB1 and -LB2, as proved by isothermal titration calorimetry. To our knowledge, this work reports for the first time the three-dimensional structures of ocellatin peptides. Copyright © 2018 Elsevier Inc. All rights reserved.

Micellar emulsions composed of mPEG-PCL/MCT as novel nanocarriers for systemic delivery of genistein: a comparative study with micelles

PubMed Central

Zhang, Tianpeng; Wang, Huan; Ye, Yanghuan; Zhang, Xingwang; Wu, Baojian

2015-01-01

Polymeric micelles receive considerable attention as drug delivery vehicles, depending on the versatility in drug solubilization and targeting therapy. However, their use invariably suffers with poor stability both in in vitro and in vivo conditions. Here, we aimed to develop a novel nanocarrier (micellar emulsions, MEs) for a systemic delivery of genistein (Gen), a poorly soluble anticancer agent. Gen-loaded MEs (Gen-MEs) were prepared from methoxy poly(ethylene glycol)-block-(ε-caprolactone) and medium-chain triglycerides (MCT) by solvent-diffusion technique. Nanocarriers were characterized by dynamic light scattering, transmission electron microscopy, and in vitro release. The resulting Gen-MEs were approximately 46 nm in particle size with a narrow distribution. Gen-MEs produced a different in vitro release profile from the counterpart of Gen-ME. The incorporation of MCT significantly enhanced the stability of nanoparticles against dilution with simulated body fluid. Pharmacokinetic study revealed that MEs could notably extend the mean retention time of Gen, 1.57- and 7.38-fold as long as that of micelles and solution formulation, respectively, following intravenous injection. Furthermore, MEs markedly increased the elimination half-life (t1/2β) of Gen, which was 2.63-fold larger than that of Gen solution. Interestingly, Gen distribution in the liver and kidney for MEs group was significantly low relative to the micelle group in the first 2 hours, indicating less perfusion in such two tissues, which well accorded with the elongated mean retention time. Our findings suggested that MEs may be promising carriers as an alternative of micelles to systemically deliver poorly soluble drugs. PMID:26491290

Effect of temperature and pH on the solubility of caseins: environmental influences on the dissociation of α(S)- and β-casein.

PubMed

Post, A E; Arnold, B; Weiss, J; Hinrichs, J

2012-04-01

Selective precipitation is a common method for the isolation of β-casein, using the different calcium sensitivities of the individual caseins and the selective solubility of β-casein at a low temperature. In previous studies, it has been indicated that the β-casein yield depends on the physicochemical characteristics of the casein raw material used for fractionation. The objective of this study was to evaluate and compare the solubility of α(S)- and β-casein in solutions of micellar casein, sodium caseinate, and calcium caseinate as a function of pH and temperature. Additionally, the solubility of isolated α(S)- and β-casein fractions in demineralized water, ultrafiltration permeate, and a calcium-depleted milk salt solution was investigated depending on the pH and temperature. Furthermore, micellar casein, sodium caseinate, and calcium caseinate were subjected to a calcium chloride-precipitation process to determine the solubility of α(S)- and β-casein in calcium chloride precipitate, which is produced during selective precipitation, as a function of temperature and pH. Generally, the temperature had only a marginal influence on the α(S)-casein solubility compared with the β-casein solubility, whereas the solubility was shown to be strongly influenced by the pH. Our results suggest that the yield of β-casein obtained during isolation by means of selective precipitation may be a result of the solubility characteristics of α(S)- and β-casein in calcium chloride precipitate. Manufacturers may consider a simple solubility experiment before the β-casein isolation process by means of selective precipitation to predict β-casein yield. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Structure Formation in Salt-Free Solutions of Amphiphilic Sulfonated Polyelectrolytes

NASA Astrophysics Data System (ADS)

Bockstaller, Michael; Koehler, Werner

2000-03-01

Self-assembled systems have long attracted attention due to their practical importance in many technical and biological fields. Dodecyl-substituted poly(para-phenylen)sulfonates (abbreviated PPPS) are highly charged polyelectrolytes which in the uncharged state have been investigated extensively and an intrinsic persistence length of 15 nm has been reported. Due to their hydrophobic side chains, PPPS are compatible with water only as micellar aggregates and tend to form supramolecular structures even at concentrations as low as 10-5mol_mon.units/l. Because of the rodlike conformation of PPPS, this self-assembly leads to aggregates of anisotropic shape. Therefore, depolarized light scattering was employed to yield complementary information about structure and dynamics of these complex fluids. Aqueous solutions of PPPS at room temperature undergo a structural transition at a critical concentration of c_crit.=0.016 g/l. This transition is characterized by a strong increase of scattered intensity in forward direction and dynamic depolarized scattering. Above c_crit. the cylindrical micelles (L=310 nm, d=3.1 nm, N_radial=12) self assembly into large ellipsoidal clusters of size in the μ m range. Due to the strong increase of depolarized scattered intensity there has to be a preferential orientation of the micelles inside those clusters, which thus represent a lyotropic mesophase. By combining static and dynamic light scattering for the low q-range as well as small angle x-ray scattering for the higher q-range it is possible to determine size and shape of each aggregation step. Decreasing the molecular weight of the PPPS has profound influence on the micellar length and hence on c_crit. which is close to the overlap concentration (c ~ 1/L^3) allowing for the observation of the polyelectrolyte effect.

Solvation Dynamics in Different Phases of the Lyotropic Liquid Crystalline System.

PubMed

Roy, Bibhisan; Satpathi, Sagar; Gavvala, Krishna; Koninti, Raj Kumar; Hazra, Partha

2015-09-03

Reverse hexagonal (HII) liquid crystalline material based on glycerol monooleate (GMO) is considered as a potential carrier for drugs and other important biomolecules due to its thermotropic phase change and excellent morphology. In this work, the dynamics of encapsulated water, which plays important role in stabilization and formation of reverse hexagonal mesophase, has been investigated by time dependent Stokes shift method using Coumarin-343 as a solvation probe. The formation of the reverse hexagonal mesophase (HII) and transformation to the L2 phase have been monitored using small-angle X-ray scattering and polarized light microscopy experiments. REES studies suggest the existence of different polar regions in both HII and L2 systems. The solvation dynamics study inside the reverse hexagonal (HII) phase reveals the existence of two different types of water molecules exhibiting dynamics on a 120-900 ps time scale. The estimated diffusion coefficients of both types of water molecules obtained from the observed dynamics are in good agreement with the measured diffusion coefficient collected from the NMR study. The calculated activation energy is found to be 2.05 kcal/mol, which is associated with coupled rotational-translational water relaxation dynamics upon the transition from "bound" to "quasi-free" state. The observed ∼2 ns faster dynamics of the L2 phase compared to the HII phase may be associated with both the phase transformation as well as thermotropic effect on the relaxation process. Microviscosities calculated from time-resolved anisotropy studies infer that the interface is almost ∼22 times higher viscous than the central part of the cylinder. Overall, our results reveal the unique dynamical features of water inside the cylinder of reverse hexagonal and inverse micellar phases.

Cloud point extraction: an alternative to traditional liquid-liquid extraction for lanthanides(III) separation.

PubMed

Favre-Réguillon, Alain; Draye, Micheline; Lebuzit, Gérard; Thomas, Sylvie; Foos, Jacques; Cote, Gérard; Guy, Alain

2004-06-17

Cloud point extraction (CPE) was used to extract and separate lanthanum(III) and gadolinium(III) nitrate from an aqueous solution. The methodology used is based on the formation of lanthanide(III)-8-hydroxyquinoline (8-HQ) complexes soluble in a micellar phase of non-ionic surfactant. The lanthanide(III) complexes are then extracted into the surfactant-rich phase at a temperature above the cloud point temperature (CPT). The structure of the non-ionic surfactant, and the chelating agent-metal molar ratio are identified as factors determining the extraction efficiency and selectivity. In an aqueous solution containing equimolar concentrations of La(III) and Gd(III), extraction efficiency for Gd(III) can reach 96% with a Gd(III)/La(III) selectivity higher than 30 using Triton X-114. Under those conditions, a Gd(III) decontamination factor of 50 is obtained.

Complex Fluids and Hydraulic Fracturing.

PubMed

Barbati, Alexander C; Desroches, Jean; Robisson, Agathe; McKinley, Gareth H

2016-06-07

Nearly 70 years old, hydraulic fracturing is a core technique for stimulating hydrocarbon production in a majority of oil and gas reservoirs. Complex fluids are implemented in nearly every step of the fracturing process, most significantly to generate and sustain fractures and transport and distribute proppant particles during and following fluid injection. An extremely wide range of complex fluids are used: naturally occurring polysaccharide and synthetic polymer solutions, aqueous physical and chemical gels, organic gels, micellar surfactant solutions, emulsions, and foams. These fluids are loaded over a wide range of concentrations with particles of varying sizes and aspect ratios and are subjected to extreme mechanical and environmental conditions. We describe the settings of hydraulic fracturing (framed by geology), fracturing mechanics and physics, and the critical role that non-Newtonian fluid dynamics and complex fluids play in the hydraulic fracturing process.

Cross-Linked Micellar Spherical Nucleic Acids from Thermoresponsive Templates

PubMed Central

2017-01-01

A one-pot synthesis of micellar spherical nucleic acid (SNA) nanostructures using Pluronic F127 as a thermoresponsive template is reported. These novel constructs are synthesized in a chemically straightforward process that involves intercalation of the lipid tails of DNA amphiphiles (CpG motifs for TLR-9 stimulation) into the hydrophobic regions of Pluronic F127 micelles, followed by chemical cross-linking and subsequent removal of non-cross-linked structures. The dense nucleic acid shell of the resulting cross-linked micellar SNA enhances their stability in physiological media and facilitates their rapid cellular internalization, making them effective TLR-9 immunomodulatory agents. These constructs underscore the potential of SNAs in regulating immune response and address the relative lack of stability of noncovalent constructs. PMID:28207251

Side-chain amino-acid-based pH-responsive self-assembled block copolymers for drug delivery and gene transfer.

PubMed

Kumar, Sonu; Acharya, Rituparna; Chatterji, Urmi; De, Priyadarsi

2013-12-10

Developing safe and effective nanocarriers for multitype of delivery system is advantageous for several kinds of successful biomedicinal therapy with the same carrier. In the present study, we have designed amino acid biomolecules derived hybrid block copolymers which can act as a promising vehicle for both drug delivery and gene transfer. Two representative natural chiral amino acid-containing (l-phenylalanine and l-alanine) vinyl monomers were polymerized via reversible addition-fragmentation chain transfer (RAFT) process in the presence of monomethoxy poly(ethylene glycol) based macro-chain transfer agents (mPEGn-CTA) for the synthesis of well-defined side-chain amino-acid-based amphiphilic block copolymers, monomethoxy poly(ethylene glycol)-b-poly(Boc-amino acid methacryloyloxyethyl ester) (mPEGn-b-P(Boc-AA-EMA)). The self-assembled micellar aggregation of these amphiphilic block copolymers were studied by fluorescence spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Potential applications of these hybrid polymers as drug carrier have been demonstrated in vitro by encapsulation of nile red dye or doxorubicin drug into the core of the micellar nanoaggregates. Deprotection of side-chain Boc- groups in the amphiphilic block copolymers subsequently transformed them into double hydrophilic pH-responsive cationic block copolymers having primary amino groups in the side-chain terminal. The DNA binding ability of these cationic block copolymers were further investigated by using agarose gel retardation assay and AFM. The in vitro cytotoxicity assay demonstrated their biocompatible nature and these polymers can serve as "smart" materials for promising bioapplications.

Micellar and analytical implications of a new potentiometric PVC sensor based on neutral ion-pair complexes of dodecylmethylimidazolium bromide-sodium dodecylsulfate.

PubMed

Sanan, Reshu; Mahajan, Rakesh Kumar

2013-03-15

With an aim to characterize the micellar aggregates of imidazolium based ionic liquids, a new potentiometric PVC sensor based on neutral ion-pair complexes of dodecylmethylimidazolium bromide-sodium dodecylsulfate (C12MeIm(+)DS(-)) has been developed. The electrode exhibited a linear response for the concentration range of 7.9×10(-5)-9.8×10(-3) M with a super-Nernstian slope of 92.94 mV/decade, a response time of 5 s and critical micellar concentration (cmc) of 10.09 mM for C12MeImBr. The performance of the electrode in investigating the cmc of C12MeImBr in the presence of two drugs [promazine hydrochloride (PMZ) and promethazine hydrochloride (PMT)] and three triblock copolymers (P123, L64 and F68) has been found to be satisfactory on comparison with conductivity measurements. Various micellar parameters have been evaluated for the binary mixtures of C12MeImBr with drugs and triblock copolymers using Clint's, Rubingh's, and Motomura's approach. Thus the electrode offers a simple, straightforward and relatively fast technique for the characterization of micellar aggregates of C12MeImBr, complementing existing conventional techniques. Further, the analytical importance of proposed C12MeIm(+)-ISE as end point indicator in potentiometric titrations and for direct determination of cationic surfactants [cetylpyridinium chloride (CPC), tetradecyltrimethylammonium bromide (TTAB), benzalkonium chloride (BC)] in some commercial products was judged by comparing statistically with classical two-phase titration methods. Copyright © 2013 Elsevier Inc. All rights reserved.

Transepithelial Transport of Curcumin in Caco-2 Cells Is significantly Enhanced by Micellar Solubilisation.

PubMed

Frank, Jan; Schiborr, Christina; Kocher, Alexa; Meins, Jürgen; Behnam, Dariush; Schubert-Zsilavecz, Manfred; Abdel-Tawab, Mona

2017-03-01

Curcumin, the active constituent of Curcuma longa L. (family Zingiberaceae), has gained increasing interest because of its anti-cancer, anti-inflammatory, anti-diabetic, and anti-rheumatic properties associated with good tolerability and safety up to very high doses of 12 g. Nanoscaled micellar formulations on the base of Tween 80 represent a promising strategy to overcome its low oral bioavailability. We therefore aimed to investigate the uptake and transepithelial transport of native curcumin (CUR) vs. a nanoscaled micellar formulation (Sol-CUR) in a Caco-2 cell model. Sol-CUR afforded a higher flux than CUR (39.23 vs. 4.98 μg min -1  cm -2 , respectively). This resulted in a higher P app value of 2.11 × 10 -6  cm/s for Sol-CUR compared to a P app value of 0.56 × 10 -6  cm/s for CUR. Accordingly a nearly 9.5 fold higher amount of curcumin was detected on the basolateral side at the end of the transport experiments after 180 min with Sol-CUR compared to CUR. The determined 3.8-fold improvement in the permeability of curcumin is in agreement with an up to 185-fold increase in the AUC of curcumin observed in humans following the oral administration of the nanoscaled micellar formulation compared to native curcumin. The present study demonstrates that the enhanced oral bioavailability of micellar curcumin formulations is likely a result of enhanced absorption into and increased transport through small intestinal epithelial cells.

Use of dynamic light scattering and small-angle X-ray scattering to characterize new surfactants in solution conditions for membrane-protein crystallization

PubMed Central

Dahani, Mohamed; Barret, Laurie-Anne; Raynal, Simon; Jungas, Colette; Pernot, Pétra; Polidori, Ange; Bonneté, Françoise

2015-01-01

The structural and interactive properties of two novel hemifluorinated surfactants, F2H9-β-M and F4H5-β-M, the syntheses of which were based on the structure and hydrophobicity of the well known dodecyl-β-maltoside (DD-β-M), are described. The shape of their micellar assemblies was characterized by small-angle X-ray scattering and their intermicellar inter­actions in crystallizing conditions were measured by dynamic light scattering. Such information is essential for surfactant phase-diagram determination and membrane-protein crystallization. PMID:26144228

Accurate and fast creep test for viscoelastic fluids using disk-probe-type and quadrupole-arrangement-type electromagnetically spinning systems

NASA Astrophysics Data System (ADS)

Hirano, Taichi; Sakai, Keiji

2017-07-01

Viscoelasticity is a unique characteristic of soft materials and describes its dynamic response to mechanical stimulations. A creep test is an experimental method for measuring the strain ratio/rate against an applied stress, thereby assessing the viscoelasticity of the materials. We propose two advanced experimental systems suitable for the creep test, adopting our original electromagnetically spinning (EMS) technique. This technique can apply a constant torque by a noncontact mechanism, thereby allowing more sensitive and rapid measurements. The viscosity and elasticity of a semidilute wormlike micellar solution were determined using two setups, and the consistency between the results was assessed.

Rapid ultrasonic and microwave-assisted micellar extraction of zingiberone, shogaol and gingerols from gingers using biosurfactants.

PubMed

Peng, Li-Qing; Cao, Jun; Du, Li-Jing; Zhang, Qi-Dong; Xu, Jing-Jing; Chen, Yu-Bo; Shi, Yu-Ting; Li, Rong-Rong

2017-09-15

Two kinds of extraction methods ultrasonic-assisted micellar extraction (UAME) and microwave-assisted micellar extraction (MAME) coupled with ultra-high performance liquid chromatography with ultraviolet detector (UHPLC-UV) were developed and evaluated for extraction and determination of zingerone, 6-gingerol, 8-gingerol, 6-shogaol and 10-gingerol in Rhizoma Zingiberis and Rhizoma Zingiberis Preparata. A biosurfactant, hyodeoxycholic acid sodium salt, was used in micellar extraction. Several experimental parameters were studied separately by a univariate method. The result indicated that the MAME was more efficient than UAME. The optimal conditions of MAME were as follows: 100mM of hyodeoxycholic acid sodium salt was used as surfactant, the irradiation time was set at 10s and the extraction temperature was set at 60°C. The validation results indicated that the limits of detection were in the range of 3.80-8.11ng/mL. The average recoveries were in the range of 87.32-103.12% for the two samples at two spiking levels. Compared with other reported methods, the proposed MAME-UHPLC-UV method was more effective, quicker (10s) and more eco-friendly. Copyright © 2017 Elsevier B.V. All rights reserved.

Micellar-shape anisometry near isotropic-liquid-crystal phase transitions

NASA Astrophysics Data System (ADS)

Itri, R.; Amaral, L. Q.

1993-04-01

Micellar phases of the sodium dodecyl (lauryl) sulfate (SLS)-water-decanol system have been studied by x-ray scattering in the isotropic (I) phase, with emphasis on the I-->hexagonal (Hα) and I-->nematic-cylindrical (Nc) lyotropic liquid-crystal phase transitions. Analysis of the scattering curves is made through modeling of the product P(q)S(q), where P(q) is the micellar form factor and S(q) is the intermicellar interference function, calculated from screened Coulombic repulsion in a mean spherical approximation. Results show that micelles grow more by decanol addition near the I-->Nc transition (anisometry ν~=3) than by increased amphiphile concentration in the binary system near the I-->Hα phase transition (ν~=2.4). These results compare well with recent theories for isotropic-liquid-crystal phase transitions.

Optimization of the separation of lysergic acid diethylamide in urine by a sweeping technique using micellar electrokinetic chromatography.

PubMed

Fang, Ching; Liu, Ju-Tsung; Lin, Cheng-Huang

2002-07-25

The separation and on-line concentrations of lysergic acid diethylamide (LSD), iso-lysergic acid diethylamide (iso-LSD) and lysergic acid N,N-methylpropylamide (LAMPA) in human urine were investigated by capillary electrophoresis-fluorescence spectroscopy using sodium dodecyl sulfate (SDS) as an anionic surfactant. A number of parameters such as buffer pH, SDS concentration, Brij-30 concentration and the content of organic solvent used in separation, were optimized. The techniques of sweeping-micellar electrokinetic chromatography (sweeping-MEKC) and cation-selective exhaustive injection-sweep-micellar electrokinetic chromatography (CSEI-sweep-MEKC) were used for determining on-line concentrations. The advantages and disadvantages of this procedure with respect to sensitivity, precision and simplicity are discussed and compared. Copyright 2002 Elsevier Science BV.

Self-organization of dendritic supermolecules, based on isocyanide-gold(I), -copper(I), -palladium(II), and -platinum(II) complexes, into micellar cubic mesophases.

PubMed

Coco, Silverio; Cordovilla, Carlos; Donnio, Bertrand; Espinet, Pablo; García-Casas, María Jesús; Guillon, Daniel

2008-01-01

First- and second-generation dendrimers with an isocyanide group as the focal functional point (CN-G(n); n: 1,2) and their corresponding organometallic complexes [MCl(CN-G(n))] (M: Au, Cu), [{CuCl(CN-G(n))2}2], and trans-[MI2(CN-G(n))2] (M: Pd, Pt) have been synthesized. The free ligands and the first-generation complexes do not show mesogenic behavior, but all of the second-generation complexes display a thermotropic micellar cubic mesophase, over a large temperature range, and some of them directly at room temperature. The structure of the mesophase consists of the packing of two, discrete polyhedral micellar aggregates in a three-dimensional cubic Im$\\bar 3$m lattice.

Design and evaluation of oral nanoemulsion drug delivery system of mebudipine.

PubMed

Khani, Samira; Keyhanfar, Fariborz; Amani, Amir

2016-07-01

A nanoemulsion drug delivery system was developed to increase the oral bioavailability of mebudipine as a calcium channel blocker with very low bioavailability profile. The impact of nano-formulation on the pharmacokinetic parameters of mebudipine in rats was investigated. Nanoemulsion formulations containing ethyl oleate, Tween 80, Span 80, polyethylene glycol 400, ethanol and deionized water were prepared using probe sonicator. The optimum formulation was evaluated for physicochemical properties, such as particle size, morphology and stability. The particle size of optimum formulation was 22.8 ± 4.0 nm. Based on the results of this study, the relative bioavailability of mebudipine nanoemulsion was enhanced by about 2.6-, 2.0- and 1.9-fold, respectively, compared with suspension, ethyl oleate solution and micellar solution. In conclusion, nanoemulsion is an interesting option for the delivery of poorly water soluble molecules, such as mebudipine.

The interfacial, emulsification and encapsulation properties of hydrophobically modified inulin.

PubMed

Kokubun, S; Ratcliffe, I; Williams, P A

2018-08-15

Octenyl- and dodecenyl succinic anhydride derivatives (OSA- and DDSA-) of inulin have been synthesised and their solution and interfacial properties have been determined and compared to a commercially available alkylated inulin, Inutec SP1. All samples formed micellar aggregates in solution above a critical concentration (critical aggregation concentration) and were able to 'dissolve' a hydrophobic dye. They were also able to form stable oil-in-water (O/W) emulsions as assessed by measurements of their droplet size as a function of time. DDSA-inulin with a high degree of substitution was found to be effective at encapsulating beta carotene using the solvent evaporation method which yielded a solid which dissolved readily in simulated gastric fluid. The results confirm the potential application of these materials in a number of areas including, drug delivery, pharmaceuticals, neutraceuticals, cosmetics and personal care. Copyright © 2018 Elsevier Ltd. All rights reserved.

Finger-like pattern formation in dilute surfactant pentaethylene glycol monododecyl ether solutions.

PubMed

Kubo, Yoshihide; Yokoyama, Yasuhiro; Tanaka, Shinpei

2013-04-07

We report here peculiar finger-like patterns observed during the phase separation process of dilute micellar pentaethylene glycol monododecyl ether solutions. The patterns were composed of parallel and periodic threads of micelle-rich domains. Prior to this pattern formation, the phase separation always started with the appearance of water-rich domains rimmed by the micelle-rich domains. It was found that these rims played a significant role in the pattern formation. We explain this pattern formation using a simple simulation model with disconnectable springs. The simulation results suggested that the spatially inhomogeneous elasticity or connectivity of a transient gel of worm-like micelles was responsible for the rim formation. The rims thus formed lead rim-induced nucleation, growth, and elongation of the domains owing to their small mobility and the elastic frustration around them. These rim-induced processes eventually produce the observed finger-like patterns.

Instabilities in wormlike micelle systems. From shear-banding to elastic turbulence.

PubMed

Fardin, M-A; Lerouge, S

2012-09-01

Shear-banding is ubiquitous in complex fluids. It is related to the organization of the flow into macroscopic bands bearing different viscosities and local shear rates and stacked along the velocity gradient direction. This flow-induced transition towards a heterogeneous flow state has been reported in a variety of systems, including wormlike micellar solutions, telechelic polymers, emulsions, clay suspensions, colloidal gels, star polymers, granular materials, or foams. In the past twenty years, shear-banding flows have been probed by various techniques, such as rheometry, velocimetry and flow birefringence. In wormlike micelle solutions, many of the data collected exhibit unexplained spatio-temporal fluctuations. Different candidates have been identified, the main ones being wall slip, interfacial instability between bands or bulk instability of one of the bands. In this review, we present experimental evidence for a purely elastic instability of the high shear rate band as the main origin for fluctuating shear-banding flows.

Formation of Polymeric Nanocubes by Self-Assembly and Crystallization of Dithiolane-Containing Triblock Copolymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Margulis, Katherine; Zhang, Xiangyi; Joubert, Lydia -Marie

Template–free fabrication of non–spherical polymeric nanoparticles is desirable for various applications, but has had limited success owing to thermodynamic favorability of sphere formation. Herein we present a simple way to prepare cubic nanoparticles of block copolymers by self–assembly from aqueous solutions at room temperature. Nanocubes with edges of 40–200 nm are formed spontaneously on different surfaces upon water evaporation from micellar solutions of triblock copolymers containing a central poly(ethylene oxide) block and terminal trimethylene carbonate/dithiolane blocks. These polymers self–assemble into 28±5 nm micelles in water. Upon drying, micelle aggregation and a kinetically controlled crystallization of central blocks evidently induce solidmore » cubic particle formation. An approach for preserving the structures of these cubes in water by thiol– or photo–induced crosslinking was developed. In conclusion, the ability to solubilize a model hydrophobic drug, curcumin, was also explored.« less

Formation of Polymeric Nanocubes by Self-Assembly and Crystallization of Dithiolane-Containing Triblock Copolymers

DOE PAGES

Margulis, Katherine; Zhang, Xiangyi; Joubert, Lydia -Marie; ...

2017-10-27

Template–free fabrication of non–spherical polymeric nanoparticles is desirable for various applications, but has had limited success owing to thermodynamic favorability of sphere formation. Herein we present a simple way to prepare cubic nanoparticles of block copolymers by self–assembly from aqueous solutions at room temperature. Nanocubes with edges of 40–200 nm are formed spontaneously on different surfaces upon water evaporation from micellar solutions of triblock copolymers containing a central poly(ethylene oxide) block and terminal trimethylene carbonate/dithiolane blocks. These polymers self–assemble into 28±5 nm micelles in water. Upon drying, micelle aggregation and a kinetically controlled crystallization of central blocks evidently induce solidmore » cubic particle formation. An approach for preserving the structures of these cubes in water by thiol– or photo–induced crosslinking was developed. In conclusion, the ability to solubilize a model hydrophobic drug, curcumin, was also explored.« less

Hg2+-reactive double hydrophilic block copolymer assemblies as novel multifunctional fluorescent probes with improved performance.

PubMed

Hu, Jinming; Li, Changhua; Liu, Shiyong

2010-01-19

We report on novel type of responsive double hydrophilic block copolymer (DHBC)-based multifunctional chemosensors to Hg(2+) ions, pH, and temperatures and investigate the effects of thermo-induced micellization on the detection sensitivity. Well-defined DHBCs bearing rhodamine B-based Hg(2+)-reactive moieties (RhBHA) in the thermo-responsive block, poly(ethylene oxide)-b-poly(N-isopropylacrylamide-co-RhBHA) (PEO-b-P(NIPAM-co-RhBHA)), were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Nonfluorescent RhBHA moieties are subjected to selective ring-opening reaction upon addition of Hg(2+) ions or lowering solution pH, producing highly fluorescent acyclic species. Thus, at room temperature PEO-b-P(NIPAM-co-RhBHA) DHBCs can serve as water-soluble multifunctional and efficient fluorescent chemosensors to Hg(2+) ions and pH. Upon heating above the lower critical solution temperature (approximately 36 degrees C) of the PNIPAM block, they self-assemble into micelles possessing P(NIPAM-co-RhBHA) cores and well-solvated PEO coronas, which were fully characterized by dynamic and static laser light scattering. It was found that the detection sensitivity to Hg(2+) ions and pH could be dramatically improved at elevated temperatures due to fluorescence enhancement of RhBHA residues in the acyclic form, which were embedded within hydrophobic cores of thermo-induced micellar aggregates. This work represents a proof-of-concept example of responsive DHBC-based multifunctional fluorescent chemosensors for the highly efficient detection of Hg(2+) ions, pH, and temperatures with tunable detection sensitivity. Compared to reaction-based small molecule Hg(2+) probes in previous literature reports, the integration of stimuli-responsive block copolymers with well-developed small molecule-based selective sensing moieties in the current study are expected to exhibit preferred advantages including enhanced detection sensitivity, water dispersibility, biocompatibility, facile incorporation into devices, and the ability of further functionalization for targeted imaging and detection.

Fundamental Characterization of the Micellar Self-Assembly of Sophorolipid Esters.

PubMed

Koh, Amanda; Todd, Katherine; Sherbourne, Ezekiel; Gross, Richard A

2017-06-13

Surfactants are ubiquitous constituents of commercial and biological systems that function based on complex structure-dependent interactions. Sophorolipid (SL) n-alkyl esters (SL-esters) comprise a group of modified naturally derived glycolipids from Candida bombicola. Herein, micellar self-assembly behavior as a function of SL-ester chain length was studied. Surface tensions as low as 31.2 mN/m and critical micelle concentrations (CMCs) as low as 1.1 μM were attained for diacetylated SL-decyl ester (dASL-DE) and SL-octyl ester, respectively. For deacetylated SL-esters, CMC values reach a lower limit at SL-ester chains above n-butyl (SL-BE, 1-3 μM). This behavior of SL-esters with increasing hydrophobic tail length is unlike other known surfactants. Diffusion-ordered spectroscopy (DOSY) and T 1 relaxation NMR experiments indicate this behavior is due to a change in intramolecular interactions, which impedes the self-assembly of SL-esters with chain lengths above SL-BE. This hypothesis is supported by micellar thermodynamics where a disruption in trends occurs at n-alkyl ester chain lengths above those of SL-BE and SL-hexyl ester (SL-HE). Diacetylated (dA) SL-esters exhibit an even more unusual trend in that CMC increases from 1.75 to 815 μM for SL-ester chain lengths of dASL-BE and dASL-DE, respectively. Foaming studies, performed to reveal the macroscopic implications of SL-ester micellar behavior, show that the observed instability in foams formed using SL-esters are due to coalescence, which highlights the importance of understanding intermicellar interactions. This work reveals that SL-esters are an important new family of green high-performing surfactants with unique structure-property relationships that can be tuned to optimize micellar characteristics.

Convection-enhanced delivery of a synthetic retinoid Am80, loaded into polymeric micelles, prolongs the survival of rats bearing intracranial glioblastoma xenografts.

PubMed

Yokosawa, Michiko; Sonoda, Yukihiko; Sugiyama, Shin-ichiro; Saito, Ryuta; Yamashita, Yoji; Nishihara, Masamichi; Satoh, Taku; Kumabe, Toshihiro; Yokoyama, Masayuki; Tominaga, Teiji

2010-08-01

Prognosis for the patients with glioblastoma, the most common malignant brain tumor, remains dismal. A major barrier to progress in treatment of glioblastoma is the relative inaccessibility of tumors to chemotherapeutic agents. Convection-enhanced delivery (CED) is a direct intracranial drug infusion technique to deliver chemotherapeutic agents to the central nervous system, circumventing the blood-brain barrier and reducing systemic side effects. CED can provide wider distribution of infused agents compared to simple diffusion. We have reported that CED of a polymeric micelle carrier system could yield a clinically relevant distribution of encapsulated agents in the rat brain. Our aim was to evaluate the efficacy of CED of polymeric micellar Am80, a synthetic agonist with high affinity to nuclear retinoic acid receptor, in a rat model of glioblastoma xenografts. We also used systemic administration of temozolomide, a DNA-alkylating agent, which has been established as the standard of care for newly diagnosed malignant glioma. U87MG human glioma cells were injected into the cerebral hemisphere of nude rats. Rats bearing U87MG xenografts were treated with CED of micellar Am80 (2.4 mg/m(2)) on day 7 after tumor implantation. Temozolomide (200 mg/m(2)/day) was intraperitoneally administered daily for 5 days, starting on day 7 after tumor implantation. CED of micellar Am80 provided significantly longer survival than the control. The combination of CED of micellar Am80 and systemic administration of temozolomide provided significantly longer survival than single treatment. In conclusion, temozolomide combined with CED of micellar Am80 may be a promising method for the treatment of malignant gliomas.

Determination of deferasirox in human plasma by short-end injection and sweeping with a field-amplified sample stacking and micellar electrokinetic chromatography.

PubMed

Lin, Hung-Ju; Hsieh, Kun-Pin; Chiou, Shyh-Shin; Kou, Hwang-Shang; Wu, Shou-Mei

2016-11-30

A field-amplified sample stacking-sweeping micellar electrokinetic chromatography with short-end injection was established for determination of deferasirox (DFX) in plasma. DFX was extracted from plasma and reconstituted with deionized water (lower conductivity solution). Capillary (effective length, 10cm) was filled with background electrolyte (40mM phosphate buffer, pH 4.5, containing 20% methanol). After sample loading from outlet end at 5psi for 15s, separation was carried out by applying high voltage at 15kV for 10min. Sodium dodecyl sulfate (SDS) was used to sweep DFX for enhancing sensitivity. The optimal CE separation conditions were 40mM phosphate buffer at pH 4.5 containing 100mM SDS and 20% methanol. The analysis time was about 3.5min for DFX. The calibration curve of DFX was ranged from 1 to 20μg/ml. The linearity (r) was more than 0.998. RSD and RE in intra- and inter-day assays were all below 12.14%. The limit of detection (LOD, S/N=3) for DFX was 0.3μg/ml. The sensitivity enhancement factor between sweeping-FASS MEKC and capillary zone electrophoresis is 3.3. Finally, the method was applied for determination of DFX in β-thalassemia patients. Copyright © 2016 Elsevier B.V. All rights reserved.

Benzyl alcohol and block copolymer micellar lithography: a versatile route to assembling gold and in situ generated titania nanoparticles into uniform binary nanoarrays.

PubMed

Polleux, Julien; Rasp, Matthias; Louban, Ilia; Plath, Nicole; Feldhoff, Armin; Spatz, Joachim P

2011-08-23

Simultaneous synthesis and assembly of nanoparticles that exhibit unique physicochemical properties are critically important for designing new functional devices at the macroscopic scale. In the present study, we report a simple version of block copolymer micellar lithography (BCML) to synthesize gold and titanium dioxide (TiO(2)) nanoarrays by using benzyl alcohol (BnOH) as a solvent. In contrast to toluene, BnOH can lead to the formation of various gold nanopatterns via salt-induced micellization of polystyrene-block-poly(vinylpyridine) (PS-b-P2VP). In the case of titania, the use of BCML with a nonaqueous sol-gel method, the "benzyl alcohol route", enables the fabrication of nanopatterns made of quasi-hexagonally organized particles or parallel wires upon aging a (BnOH-TiCl(4)-PS(846)-b-P2VP(171))-containing solution for four weeks to grow TiO(2) building blocks in situ. This approach was found to depend mainly on the relative lengths of the polymer blocks, which allows nanoparticle-induced micellization and self-assembly during solvent evaporation. Moreover, this versatile route enables the design of uniform and quasi-ordered gold-TiO(2) binary nanoarrays with a precise particle density due to the absence of graphoepitaxy during the deposition of TiO(2) onto gold nanopatterns. © 2011 American Chemical Society

Shuffling cross-validation-bee algorithm as a new descriptor selection method for retention studies of pesticides in biopartitioning micellar chromatography.

PubMed

Zarei, Kobra; Atabati, Morteza; Ahmadi, Monire

2017-05-04

Bee algorithm (BA) is an optimization algorithm inspired by the natural foraging behaviour of honey bees to find the optimal solution which can be proposed to feature selection. In this paper, shuffling cross-validation-BA (CV-BA) was applied to select the best descriptors that could describe the retention factor (log k) in the biopartitioning micellar chromatography (BMC) of 79 heterogeneous pesticides. Six descriptors were obtained using BA and then the selected descriptors were applied for model development using multiple linear regression (MLR). The descriptor selection was also performed using stepwise, genetic algorithm and simulated annealing methods and MLR was applied to model development and then the results were compared with those obtained from shuffling CV-BA. The results showed that shuffling CV-BA can be applied as a powerful descriptor selection method. Support vector machine (SVM) was also applied for model development using six selected descriptors by BA. The obtained statistical results using SVM were better than those obtained using MLR, as the root mean square error (RMSE) and correlation coefficient (R) for whole data set (training and test), using shuffling CV-BA-MLR, were obtained as 0.1863 and 0.9426, respectively, while these amounts for the shuffling CV-BA-SVM method were obtained as 0.0704 and 0.9922, respectively.

Chiral micellar electrokinetic chromatography (CMEKC)-atmospheric pressure photoionization of benzoin derivatives using mixed molecular micelles

PubMed Central

He, Jun; Shamsi, Shahab A.

2012-01-01

In the present work we report, for the first time, the successful on-line coupling of chiral micellar electrokinetic chromatography (CMEKC) to atmospheric pressure photo-ionization mass spectrometry (APPI-MS). Four structurally similar neutral test solutes (e.g., benzoin derivatives) were successfully ionized by APPI-MS. The mass spectra in the positive ion mode showed that the protonated molecular ions of benzoins are not the most abundant fragment ions. Simultaneous enantioseparation by CMEKC and on-line APPI-MS detection of four photoinitiators: hydrobenzoin (HBNZ), benzoin (BNZ), benzoin methyl ether (BME), benzoin ethyl ether (BEE), were achieved using an optimized molar ratio of mixed molecular micelle of two polymeric chiral surfactants (polysodium N-undecenoxy carbonyl-L-leucinate and polysodium N-undecenoyl-L,L-leucylvalinate). The CMEKC conditions, such as voltage, chiral polymeric surfactant concentration, buffer pH, and BGE concentration, were optimized using a multivariate central composite design (CCD). The sheath liquid composition (involving % v/v methanol, dopant concentration, electrolyte additive concentration, and flow rate) and spray chamber parameters (drying gas flow rate, drying gas temperature, and vaporizer temperature) were also optimized with CCD. Models built based on the CCD results and response surface method was used to analyze the interactions between factors and their effects on the responses. The final overall optimum conditions for CMEKC-APPI-MS were also predicted and found in agreement with the experimentally optimized parameters. PMID:21500208

Determination of lysergic acid diethylamide (LSD) in mouse blood by capillary electrophoresis/ fluorescence spectroscopy with sweeping techniques in micellar electrokinetic chromatography.

PubMed

Fang, Ching; Liu, Ju-Tsung; Chou, Shiu-Huey; Lin, Cheng-Huang

2003-03-01

The separation and on-line concentration of lysergic acid diethylamide (LSD) in mouse blood was achieved by means of capillary electrophoresis/fluorescence spectroscopy using sodium dodecyl sulfate (SDS) as the surfactant. Techniques involving on-line sample concentration, including sweeping micellar electrokinetic chromatography (sweeping-MEKC) and cation-selective exhaustive injection-sweep-micellar electrokinetic chromatography (CSEI-sweep-MEKC) were applied; the optimum on-line concentration and separation conditions were determined. In the analysis of an actual sample, LSD was found in a blood sample from a test mouse (0.1 mg LSD fed to a 20 g mouse; approximately 1/10 to the value of LD(50)). As a result, 120 and 30 ng/mL of LSD was detected at 20 and 60 min, respectively, after ingestion of the doses.

Imparting in situ stability to displacing fluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.

1970-07-14

An aqueous preslug containing electrolyte an/or isopropanol was injected before a micellar-polymer flood to inhibit the tendency of the formation to degrade the flood. Berea cores were saturated with water from Henry lease in Illinois (18,000 ppm TDS), flooded with Henry crude (7 cp viscosity at 72/sup 0/F, specific gravity 0.843), and waterflooded with Henry water. A recovery of 86.3 percent OIP was obtained with the following preslug, micellar slug, and polymer flood. The preslug contained water from the water reservoir in Palestine, Illinois (400 ppm TDS) and sodium hydroxide. Ammonium petroleum sulfonate, Henry crude, isopropanol, nonyl phenol, sodium hydroxide,more » and Palestine water were combined to form the water-external micellar slug. The polymer flood was composed of Pusher 530, Palestine water, isopropanol, and ammonium thiocyanide.« less

Chemometric Deconvolution of Continuous Electrokinetic Injection Micellar Electrokinetic Chromatography Data for the Quantitation of Trinitrotoluene in Mixtures of Other Nitroaromatic Compounds

DTIC Science & Technology

2014-02-24

Suite 600 Washington, DC 20036 NRL/MR/ 6110 --14-9521 Approved for public release; distribution is unlimited. 1Science & Engineering Apprenticeship...Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/ 6110 --14-9521 Chemometric Deconvolution of Continuous Electrokinetic Injection Micellar... Engineering Apprenticeship Program American Society for Engineering Education Washington, DC Kevin Johnson Navy Technology Center for Safety and

Probing the amphiphile micellar to hexagonal phase transition using Positron Annihilation Lifetime Spectroscopy.

PubMed

Dong, Aurelia W; Fong, Celesta; Hill, Anita J; Boyd, Ben J; Drummond, Calum J

2013-07-15

Positron Annihilation Lifetime Spectroscopy (PALS) has been utilised only sparingly for structural characterisation in self assembled materials. Inconsistencies in approaches to experimental configuration and data analysis between studies has complicated comparisons between studies, meaning that the technique has not provided a cohesive data set across the study of different self assembled systems that advance the technique towards an important tool in soft matter research. In the current work a systematic study was conducted using ionic and non-ionic micellar systems with increasing surfactant concentration to probe positron behaviour on changes between micellar phase structures, and data analysed using contemporary approaches to fit four component spectra. A characteristic orthopositronium lifetime (in the organic regions) of 3.5±0.2 ns was obtained for the hexagonal phase for surfactants with C12 alkyl chains. Chemical quenching of the positron species was also observed for systems with ionic amphiphiles. The application of PALS has also highlighted an inconsistency in the published phase diagram for the octa(ethylene oxide) monododecyl ether (C12EO8) system. These results provide new insight into how the physical properties of micellar systems can be related to PALS parameters and means that the PALS technique can be applied to other more complex self-assembled amphiphile systems. Copyright © 2013 Elsevier Inc. All rights reserved.

TR-ESR Investigation on Reaction of Vitamin C with Excited Triplet of 9,10-phenanthrenequinone in Reversed Micelle Solutions

NASA Astrophysics Data System (ADS)

Xu, Xin-sheng; Shi, Lei; Liu, Yi; Ji, Xue-han; Cui, Zhi-feng

2011-04-01

Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C (VC) and the triplet excited states of 9,10-phenanthrenequinone (PAQ) in ethylene glycol-water (EG-H2O) homogeneous and inhomogeneous reversed micelle solutions. Reversed micelle solutions were used to be the models of physiological environment of biological cell and tissue. In PAQ/EG-H2O homogeneous solution, the excited triplet of PAQ (3PAQ*) abstracts hydrogen atom from solvent EG. In PAQ/VC/EG-H2O solution, 3PAQ* abstracts hydrogen atom not only from solvent EG but also from VC. The quenching rate constant of 3PAQ* by VC is close to the diffusion-controlled value of 1.41 × 108 L/(mol ·s). In hexadecyltrimethylammonium bromide (CTAB)/EG-H2O and aerosol OT (AOT)/EG-H2O reversed micelle solutions, 3PAQ* and VC react around the water-oil interface of the reversed micelle. Exit of 3PAQ* from the lipid phase slows down the quenching reaction. For Triton X-100 (TX-100)/EG-H2O reversed micelle solution, PAQ and VC coexist inside the hydrophilic polyethylene glycol core, and the quenching rate constant of 3PAQ* by VC is larger than those in AOT/EG-H2O and CTAB/EG-H2O reversed micelle solutions, even a little larger than that in EG-H2O homogeneous solution. The strong emissive chemically induced dynamic electron polarization of As.- resulted from the effective TM spin polarization transfer in hydrogen abstraction of 3PAQ* from VC.

Mechanism of Resilin Elasticity

PubMed Central

Qin, Guokui; Hu, Xiao; Cebe, Peggy; Kaplan, David L.

2012-01-01

Resilin is critical in the flight and jumping systems of insects as a polymeric rubber-like protein with outstanding elasticity. However, insight into the underlying molecular mechanisms responsible for resilin elasticity remains undefined. Here we report the structure and function of resilin from Drosophila CG15920. A reversible beta-turn transition was identified in the peptide encoded by exon III and for full length resilin during energy input and release, features that correlate to the rapid deformation of resilin during functions in vivo. Micellar structures and nano-porous patterns formed after beta-turn structures were present via changes in either the thermal or mechanical inputs. A model is proposed to explain the super elasticity and energy conversion mechanisms of resilin, providing important insight into structure-function relationships for this protein. Further, this model offers a view of elastomeric proteins in general where beta-turn related structures serve as fundamental units of the structure and elasticity. PMID:22893127

Reverse Micelle Based Synthesis of Microporous Materials in Microgravity

NASA Technical Reports Server (NTRS)

Dutta, Prabir K.

1995-01-01

Formation of zincophosphates from zinc and phosphate containing reverse micelles (water droplets in hexane) has been examined. The frameworks formed resemble that made by conventional hydrothermal synthesis. Dynamics of crystal growth are however quite different, and form the main focus of this study. In particular, the formation of zincophosphate with the sodalite framework was examined in detail. The intramicellar pH was found to have a strong influence on crystal growth. Crystals with a cubic morphology were formed directly from the micelles, without an apparent intermediate amorphous phase over a period of four days by a layer-bylayer growth at the intramicellar pH of 7.6. At a pH of 6.8, an amorphous precipitate rapidly sediments in hours. Sodalite was eventually formed from this settled phase via surface diffusion and reconstruction within four days. With a rotating cell, it was possible to minimize sedimentation and crystals were found to grow epitaxially from the spherical, amorphous particles. Intermediate pH's of 7.2 led to formation of aggregated sodalite crystals prior to settling, again without any indication of an intermediate amorphous phase. These diverse pathways were possible due to changes in intramicellar supersaturation conditions by minor changes in pH. In contrast, conventional syntheses in this pH range all proceeded by similar crystallization pathways through an amorphous gel. This study establishes that synthesis of microporous frameworks is not only possible in reverse micellar systems, but they also allow examination of possible crystallization pathways.

The influence of NaCl on hydrophobicity of selected, pharmacologically active bile acids expressed with chromatographic retention index and critical micellar concentration.

PubMed

Posa, Mihalj; Pilipović, Ana; Lalić, Mladena

2010-11-01

Many of bile acids' (BA) physiological properties, as receptor binding, activation of ionic channels, binding to blood proteins, etc. are due to their hydrophobicity. On the other hand, hydrophobicity determines BAs' physico-chemical characteristics as micelle forming and adsorption (surface activity). However, BA hydrophobicity is not determined solely by their structure. Medium composition, especially the concentration of electrolytes has influence on BA hydrophobicity. Thus, the objective of this work was to examine the effect of NaCl on hydrophobicity of selected bile acids. This influence is specified with the retention factor k (reversed phase high pressure liquid chromatography (RPHPLC)) and critical micellar concentration (CMC) determined by non-invasive NMR method. The value of lnk elevates with the increase in mobile phase NaCl concentration i.e. Deltalnk/Deltac(NaCl) depends on the number of water molecules not stabilised by hydrogen bonds in bile acid hydration sheath. For bile acids that contain hydroxyl groups (except those with beta equatorial hydroxyl groups) the value of |DeltalnCMC/Deltac(NaCl)| rises with the increase in the number of non-stabilized water molecules in their hydration sheath. Even though oxo derivatives of cholic acid have similar chromatographic parameters they behave differently when it comes to CMC. In fact with the introduction of oxo groups the value of its |DeltalnCMC/Deltac(NaCl)| elevates but it results in a decrease in the number of non-stabilized water molecules i.e. hydrophobicity falls. Different behaviour of oxo derivatives implicate that, besides "hydrophobic interactions" in their micelles, there are also hydrogen bonds i.e. fiord effect exists. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Several reverse-time integrable nonlocal nonlinear equations: Rogue-wave solutions

NASA Astrophysics Data System (ADS)

Yang, Bo; Chen, Yong

2018-05-01

A study of rogue-wave solutions in the reverse-time nonlocal nonlinear Schrödinger (NLS) and nonlocal Davey-Stewartson (DS) equations is presented. By using Darboux transformation (DT) method, several types of rogue-wave solutions are constructed. Dynamics of these rogue-wave solutions are further explored. It is shown that the (1 + 1)-dimensional fundamental rogue-wave solutions in the reverse-time NLS equation can be globally bounded or have finite-time blowing-ups. It is also shown that the (2 + 1)-dimensional line rogue waves in the reverse-time nonlocal DS equations can be bounded for all space and time or develop singularities in critical time. In addition, the multi- and higher-order rogue waves exhibit richer structures, most of which have no counterparts in the corresponding local nonlinear equations.

Comparison of the rates of ozonation of biological antioxidants and oleate and linoleate esters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giamalva, D.; Church, D.F.; Pryor, W.A.

1985-12-17

The rates of reaction with ozone of some biological antioxidants and simple polyunsaturated fatty acids (PUFA) have been measured in water or in aqueous micellar solutions. At pH 7.0 the rate constants are ca. 10(6) M-1 sec-1 for urate, alpha-tocopherol, and PUFA, and 6 X 10(7) M-1 sec-1 for ascorbate. When ozone-containing air is breathed, ascorbate in the lung may undergo direct ozonation. However, alpha-tocopherol is probably spared direct reaction with ozone because it doesn't effectively compete with PUFA in pulmonary membranes; rather, tocopherol is used to scavenge radicals produced from the ozone-PUFA reaction.

Cyclodextrin-modified MEKC for enantioseparation of hexaconazole, penconazole, and myclobutanil.

PubMed

Wan Ibrahim, Wan Aini; Hermawan, Dadan; Sanagi, M Marsin; Aboul-Enein, Hassan Y

2009-02-01

A CD-modified micellar EKC (CD-MEKC) method with 2-hydroxypropyl-gamma-CD (HP-gamma-CD) as chiral selector for the enantioseparation of three chiral triazole fungicides, namely hexaconazole, penconazole, and myclobutanil, is reported for the first time. Simultaneous enantioseparation of the three triazole fungicides was successfully achieved using a CD-MEKC system containing 40 mM HP-gamma-CD and 50 mM SDS in 25 mM phosphate buffer (pH 3.0) solution with resolutions (R(s)) greater than 1.60, peak efficiencies (N) greater than 200,000 for all enantiomers and an analysis time within 15 min compared to 36 min as previously reported using sulfated-beta-CD.

Deracemization of bilirubin as the marker of the chirality of micellar aggregates.

PubMed

Sorrenti, Alessandro; Altieri, Barbara; Ceccacci, Francesca; Di Profio, Pietro; Germani, Raimondo; Giansanti, Luisa; Savelli, Gianfranco; Mancini, Giovanna

2012-01-01

The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities. Copyright © 2011 Wiley-Liss, Inc.

Recent Progress in Functional Micellar Carriers with Intrinsic Therapeutic Activities for Anticancer Drug Delivery.

PubMed

Qu, Ying; Chu, BingYang; Shi, Kun; Peng, JinRong; Qian, ZhiYong

2017-12-01

Polymeric micelles have presented superior delivery properties for poorly water-soluble chemotherapeutic agents. However, it remains discouraging that there may be some additional short or long-term toxicities caused by the metabolites of high quantities of carriers. If carriers had simultaneous therapeutic effects with the drug, these issues would not be a concern. For this, carriers not only simply act as drug carriers, but also exert an intrinsic therapeutic effect as a therapeutic agent. The functional micellar carriers would be beneficial to maximize the anticancer effect, overcome the drug resistance and reduce the systemic toxicity. In this review, we aim to summarize the recent progress on the development of functional micellar carriers with intrinsic anticancer activities for the delivery of anticancer drugs. This review focuses on the design strategies, properties of carriers and the drug loading behavior. In addition, the combinational therapeutic effects between carriers and chemotherapeutic agents are also discussed.

Analysis of different beta-lactams antibiotics in pharmaceutical preparations using micellar electrokinetic capillary chromatography.

PubMed

Pérez, M I Bailón; Rodríguez, L Cuadros; Cruces-Blanco, C

2007-01-17

The potential of micellar electrokinetic capillary chromatography (MEKC) for analyzing nine beta-lactams antibiotics (cloxacillin, dicloxacillin, oxacillin, penicillin G, penicillin V, ampicillin, nafcillin, piperacillin, amoxicillin) in different pharmaceutical preparations, have been demonstrated. An experimental design strategy has been applied to optimize the main variables: pH and buffer concentration, concentration of the micellar medium, separation voltage and capillary temperature. Borate buffer (26mM) at pH 8.5 containing 100mM sodium dodecyl sulphate (SDS) was used as the background electrolyte. The method was validated. Linearity, limit of detection and quantitation and precision were established for each compound. The analysis of some of the beta-lactams in Orbenin capsules, Britapen tables and in Veterin-Micipen injectable, all used in human and veterinary medicine, have demonstrated the applicability of these technique for quality control in the pharmaceutical industry.

Effect of nucleoside analogue antimetabolites on the structure of PEO–PPO–PEO micelles investigated by SANS

DOE PAGES

Han, Youngkyu; Zhang, Zhe; Smith, Gregory S.; ...

2017-04-19

In this work, the effect of three nucleoside analogue antimetabolites (5-fluorouracil, floxuridine, and gemcitabine) on the structure of Pluronic L62 copolymer micelles was investigated using small-angle neutron scattering. These antimetabolites used for cancer chemotherapy have analogous molecular structures but different molecular sizes and aqueous solubilities. It was found that the addition of the three antimetabolites slightly reduced the micellar size and aggregation number, and the micellar anisotropy. The added antimetabolites also changed the internal molecular distribution of the micelles as measured by the scattering length densities, resulting in enhanced hydration of the hydrophobic core region of the micelle. The strengthmore » of the effect was found to correlate with the molecular properties of the model drugs, i.e. a larger molecular size and a higher aqueous solubility lead to enhanced hydration of the micellar core.« less

Spin label studies of micellar and pre-micellar aggregates.

PubMed

Ernades, J R; Schreier, S; Chaimovich, H

1976-02-01

Micelles of hexadecyl trimethyl ammonium bromide (CTABr) have been investigated with the use of a faty acid spin label and its methyl ester derivative. The esr * spectra provided information about the degree of motion of the probes in the micelles as evaluated from calculation of rotational correlation times. Evidence is presented for the formation of pre-micellar aggregates at concentrations below the cmc. The effect of addition of thiophenoxide on the structure of CTABr micelles was to decrease the rate of motion of the spin probes, probably due to a tighter packing of the hydrophobic core as a consequence of charge neutralization at the micelle surface by the substrate. Decreasing values of the isotropic hyperfine splitting of the spin probe with increasing concentration of thiophenoxide were taken as indicating that the latter causes a decrease of the degree of hydration of the polar head region of the detergent.

Effect of nucleoside analogue antimetabolites on the structure of PEO–PPO–PEO micelles investigated by SANS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Youngkyu; Zhang, Zhe; Smith, Gregory S.

2017-01-01

The effect of three nucleoside analogue antimetabolites (5-fluorouracil, floxuridine, and gemcitabine) on the structure of Pluronic L62 copolymer micelles was investigated using small-angle neutron scattering. These antimetabolites used for cancer chemotherapy have analogous molecular structures but different molecular sizes and aqueous solubilities. It was found that the addition of the three antimetabolites slightly reduced the micellar size and aggregation number, and the micellar anisotropy. The added antimetabolites also changed the internal molecular distribution of the micelles as measured by the scattering length densities, resulting in enhanced hydration of the hydrophobic core region of the micelle. The strength of the effectmore » was found to correlate with the molecular properties of the model drugs, i.e. a larger molecular size and a higher aqueous solubility lead to enhanced hydration of the micellar core.« less

Supercritical fluid reverse micelle separation

DOEpatents

Fulton, John L.; Smith, Richard D.

1993-01-01

A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W.sub.o that determines the maximum size of the reverse micelles. The maximum ratio W.sub.o of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions.

Supercritical fluid reverse micelle separation

DOEpatents

Fulton, J.L.; Smith, R.D.

1993-11-30

A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W[sub o] that determines the maximum size of the reverse micelles. The maximum ratio W[sub o] of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions. 27 figures.

Observation of small cluster formation in concentrated monoclonal antibody solutions and its implications to solution viscosity.

PubMed

Yearley, Eric J; Godfrin, Paul D; Perevozchikova, Tatiana; Zhang, Hailiang; Falus, Peter; Porcar, Lionel; Nagao, Michihiro; Curtis, Joseph E; Gawande, Pradad; Taing, Rosalynn; Zarraga, Isidro E; Wagner, Norman J; Liu, Yun

2014-04-15

Monoclonal antibodies (mAbs) are a major class of biopharmaceuticals. It is hypothesized that some concentrated mAb solutions exhibit formation of a solution phase consisting of reversibly self-associated aggregates (or reversible clusters), which is speculated to be responsible for their distinct solution properties. Here, we report direct observation of reversible clusters in concentrated solutions of mAbs using neutron spin echo. Specifically, a stable mAb solution is studied across a transition from dispersed monomers in dilute solution to clustered states at more concentrated conditions, where clusters of a preferred size are observed. Once mAb clusters have formed, their size, in contrast to that observed in typical globular protein solutions, is observed to remain nearly constant over a wide range of concentrations. Our results not only conclusively establish a clear relationship between the undesirable high viscosity of some mAb solutions and the formation of reversible clusters with extended open structures, but also directly observe self-assembled mAb protein clusters of preferred small finite size similar to that in micelle formation that dominate the properties of concentrated mAb solutions. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Photodegradation mechanism and rate improvement of chlorinated aromatic dye in non-ionic surfactant solutions.

PubMed

Ma, C W; Chu, W

2001-07-01

A typical insoluble chlorinated aromatic dye (CAD), disperse red (DR), was used to explore the reaction mechanism and kinetics of photodegradation in non-ionic surfactant solutions. The use of an additional hydrogen source and photosensitizer is also studied to improve the decay rates. The decay rate of dye in surfactants depends on the Km of surfactants and their ability to offering an effective hydrogen source. The photodegradation of CAD can be divided into three stages: the initial lag stage. the fast degradation stage and the final retardation stage. The lag stage will vanish and the decay rates of dye can be greatly improved by 2.5-3.6 times after adding an additional hydrogen source (NaBH4) or photosensitizer (acetone) to the surfactant micellar solution. However, the use of an additional hydrogen source or photosensitizer has dosage limitations in such applications. The photoreduction of DR is the main reaction mechanism, in which photodechlorination is observed first with the generation of HCI as the final product, then followed by photodecolorization by breaking the azo bond of the chromophore.

An NMR (Nuclear Magnetic Resonance) Investigation of the Chemical Association and Molecular Dynamics in Asphalt Ridge Tar Sand Ore and Bitumen

DOE R&D Accomplishments Database

Netzel, D. A.; Coover, P. T.

1987-09-01

Preliminary studies on tar sand bitumen given in this report have shown that the reassociation of tar sand bitumen to its original molecular configuration after thermal stressing is a first-order process requiring nearly a week to establish equilibrium. Studies were also conducted on the dissolution of tar sand bitumen in solvents of varying polarity. At a high-weight fraction of solute to solvent the apparent molecular weight of the bitumen molecules was greater than that of the original bitumen when dissolved in chloroform-d{sub 1} and benzene-d{sub 6}. This increase in the apparent molecular weight may be due to micellar formation or a weak solute-solvent molecular complex. Upon further dilution with any of the solvents studied, the apparent molecular weight of the tar sand bitumen decreased because of reduced van der Waals forces of interaction and/or hydrogen bonding. To define the exact nature of the interactions, it will be necessary to have viscosity measurements of the solutions.

Adiabatic model of field reversal by fast ions in an axisymmetric open trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsidulko, Yu. A., E-mail: tsidulko@mail.ru

2016-06-15

A model of field reversal by fast ions has been developed under the assumption of preservation of fast-ion adiabatic invariants. Analytical solutions obtained in the approximation of a narrow fast-ion layer and numerical solutions to the evolutionary problem are presented. The solutions demonstrate the process of formation of a field reversed configuration with parameters close to those of the planned experiment.

Measurement of Nitroaromatic Explosives by Micellar Electrokinetic Chromatography in Waters Collected Along a Tropical Estuary

DTIC Science & Technology

2014-02-07

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/ 6110 --14-9504 Measurement of Nitroaromatic Explosives by Micellar Electrokinetic...Carolina CaMeron lindsay Science & Engineering Apprenticeship Program Office of Naval Research Arlington, Virginia i REPORT DOCUMENTATION PAGE Form...GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 2 . REPORT TYPE1. REPORT DATE (DD-MM-YYYY) 4. TITLE

Estimation of carotenoid bioavailability from fresh stir-fried vegetables using an in vitro digestion/Caco-2 cell culture model.

PubMed

Garrett; Failla; Sarama

2000-11-01

We previously developed an in vitro model to estimate the relative bioavailability of carotenoids from a meal prepared using commercial baby foods. The general applicability of this model was tested using a stir-fried meal consisting of fresh spinach, fresh carrots, tomato paste, and vegetable oil. After in vitro digestion of the cooked meal, the aqueous fraction was separated from residual oil droplet and solids by centrifugation to quantify micellarized carotenoids. The percentages of lutein, lycopene, alpha-carotene, and beta-carotene transferred from the meal to the micellar fraction were 29.0 +/- 0.6, 3.2 +/- 0.1, 14.7 +/- 0.3, and 16.0 +/- 0.4, respectively. Carotenoid transfer from the meal to the aqueous fraction was inhibited when bile extract was omitted from the intestinal phase of digestion. The bioavailability of the micellarized carotenoids was validated using differentiated cultures of Caco-2 human intestinal cells. All four carotenoids were accumulated in a linear manner throughout a 6-hr incubation period. Metabolic integrity was not compromised by exposure of cultures to the diluted aqueous fraction from the digested meal. The addition of 500 µmol/L alpha-tocopherol to test medium significantly improved the stability of the micellar carotenoids within the tissue culture environment. These results support the utility of the in vitro digestion procedure for estimating the bioavailability of carotenoids from foods and meals.

Micelles As Delivery System for Cancer Treatment.

PubMed

Keskin, Dilek; Tezcaner, Aysen

2017-01-01

Micelles are nanoparticles formed by the self-assembly of amphiphilic block copolymers in certain solvents above concentrations called critical micelle concentration (CMC). Micelles are used in different fields like food, cosmetics, medicine, etc. These nanosized delivery systems are under spotlight in the recent years with new achievements in terms of their in vivo stability, ability to protect entrapped drug, release kinetics, ease of cellular penetration and thereby increased therapeutic efficacy. Drug loaded micelles can be prepared by dialysis, oil-in-water method, solid dispersion, freezing, spray drying, etc. The aim of this review is to give an overview of the research on micelles (in vitro, in vivo and clinical) as delivery system for cancer treatment. Passive targeting is one route for accumulation of nanosized micellar drug formulations. Many research groups from both academia and industry focus on developing new strategies for improving the therapeutic efficacy of micellar systems (active targeting to the tumor site, designing multidrug delivery systems for overcoming multidrug resistance or micelles formed by prodrug conjugates, etc). There is only one micellar drug formulation in South Korea that has reached clinical practice. However, there are many untargeted anticancer drug loaded micellar formulations in clinical trials, which have potential for use in clinics. Many more products are expected to be on the market in the near future. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Lipoamino acid-based micelles as promising delivery vehicles for monomeric amphotericin B.

PubMed

Serafim, Cláudia; Ferreira, Inês; Rijo, Patrícia; Pinheiro, Lídia; Faustino, Célia; Calado, António; Garcia-Rio, Luis

2016-01-30

Lipoamino acid-based micelles have been developed as delivery vehicles for the hydrophobic drug amphotericin B (AmB). The micellar solubilisation of AmB by a gemini lipoamino acid (LAA) derived from cysteine and its equimolar mixtures with the bile salts sodium cholate (NaC) and sodium deoxycholate (NaDC), as well as the aggregation sate of the drug in the micellar systems, was studied under biomimetic conditions (phosphate buffered-saline, pH 7.4) using UV-vis spectroscopy. Pure surfactant systems and equimolar mixtures were characterized by tensiometry and important parameters were determined, such as critical micelle concentration (CMC), surface tension at the CMC (γCMC), maximum surface excess concentration (Γmax), and minimum area occupied per molecule at the water/air interface (Amin). Rheological behaviour from viscosity measurements at different shear rates was also addressed. Solubilisation capacity was quantified in terms of molar solubilisation ratio (χ), micelle-water partition coefficient (KM) and Gibbs energy of solubilisation (ΔGs°). Formulations of AmB in micellar media were compared in terms of drug loading, encapsulation efficiency, aggregation state of AmB and in vitro antifungal activity against Candida albicans. The LAA-containing micellar systems solubilise AmB in its monomeric and less toxic form and exhibit in vitro antifungal activity comparable to that of the commercial formulation Fungizone. Copyright © 2015 Elsevier B.V. All rights reserved.

The Oral Bioavailability of Trans-Resveratrol from a Grapevine-Shoot Extract in Healthy Humans is Significantly Increased by Micellar Solubilization.

PubMed

Calvo-Castro, Laura A; Schiborr, Christina; David, Franziska; Ehrt, Heidi; Voggel, Jenny; Sus, Nadine; Behnam, Dariush; Bosy-Westphal, Anja; Frank, Jan

2018-05-01

Grapevine-shoot extract Vineatrol30 contains abundant resveratrol monomers and oligomers with health-promoting potential. However, the oral bioavailability of these compounds in humans is low (˂1-2%). The aim of this study was to improve the oral bioavailability of resveratrol from vineatrol by micellar solubilization. Twelve healthy volunteers (six women, six men) randomly ingested a single dose of 500 mg vineatrol (30 mg trans-resveratrol, 75 mg trans-ε-viniferin) as native powder or liquid micelles. Plasma and urine were collected at baseline and over 24 h after intake. Resveratrol and viniferin were analyzed by HPLC. The area under the plasma concentration-time curve (AUC) and mean maximum plasma trans-resveratrol concentrations were 5.0-fold and 10.6-fold higher, respectively, after micellar supplementation relative to the native powder. However, no detectable amounts of trans-ε-viniferin were found in either plasma or urine. The transepithelial permeability of trans-resveratrol and trans-ε-viniferin across differentiated Caco-2 monolayers was consistent to the absorbed fractions in vivo. The oral bioavailability of trans-resveratrol from the grapevine-shoot extract Vineatrol30 was significantly increased using a liquid micellar formulation, without any treatment-related adverse effects, making it a suitable system for improved supplementation of trans-resveratrol. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Extraction and separation of tungsten (VI) from aqueous media with Triton X-100-ammonium sulfate-water aqueous two-phase system without any extractant.

PubMed

Yongqiang Zhang; Tichang Sun; Tieqiang Lu; Chunhuan Yan

2016-11-25

An aqueous two-phase system composed of Triton X-100-(NH 4 ) 2 SO 4 -H 2 O was proposed for extraction and separation of tungsten(VI) from aqueous solution without using any extractant. The effects of aqueous pH, concentration of ammonium sulfate, Triton X-100 and tungsten, extracting temperature on the extraction of tungsten were investigated. The extraction of tungsten has remarkable relationship with aqueous pH and are to above 90% at pH=1.0-3.0 under studied pH range (pH=1.0-7.0) and increases gradually with increasing Triton X-100 concentration, but decreases slightly with increasing ammonium sulfate concentration. The extraction percentage of tungsten is hardly relevant to temperature but its distribution coefficient linearly increases with increasing temperature within 303.15-343.15K. The distribution coefficient of tungsten increases with the increase of initial tungsten concentration (0.1-3%) and temperature (303.15 K-333.15K). The solubilization capacity of tungsten in Triton X-100 micellar phase is independent of temperature. FT-IR analysis reveals that there is no evident interaction between polytungstate anion and ether oxygen unit in Triton X-100, and DLS analysis indicates that zeta potential of Triton X-100 micellar phase have a little change from positive to negative after extracting tungsten. Based on the above-mentioned results, it can be deduced that polytungstate anions are solubilized in hydrophilic outer shell of Triton X-100 micelles by electrostatic attraction depending on its relatively high hydrophobic nature. The stripping of tungsten is mainly influenced by temperature and can be easily achieved to 95% in single stage stripping. The tungsten (VI) is separated out from solution containing Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Al(III), Cr(III) and Mn(II) under the suitable conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis and Characterization of Cleavable Core-Cross-Linked Micelles Based on Amphiphilic Block Copolypeptoids as Smart Drug Carriers.

PubMed

Li, Ang; Zhang, Donghui

2016-03-14

Amphiphilic block copolypeptoids consisting of a hydrophilic poly(N-ethyl glycine) segment and a hydrophobic poly[(N-propargyl glycine)-r-(N-decyl glycine)] random copolymer segment [PNEG-b-P(NPgG-r-NDG), EPgD] have been synthesized by sequential primary amine-initiated ring-opening polymerization (ROP) of the corresponding N-alkyl N-carboxyanhydride monomers. The block copolypeptoids form micelles in water and the micellar core can be cross-linked with a disulfide-containing diazide cross-linker by copper-mediated alkyne-azide cycloaddition (CuAAC) in aqueous solution. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis revealed the formation of spherical micelles with uniform size for both the core-cross-linked micelles (CCLMs) and non-cross-linked micelles (NCLMs) precursors for selective block copolypeptoid polymers. The CCLMs exhibited increased dimensional stability relative to the NCLMs in DMF, a nonselective solvent for the core and corona segments. Micellar dissociation of CCLMs can be induced upon addition of a reducing agent (e.g., dithiothreitol) in dilute aqueous solutions, as verified by a combination of fluorescence spectroscopy, size exclusion chromatography (SEC), and (1)H NMR spectroscopic measurement. Doxorubicin (DOX), an anticancer drug, can be loaded into the hydrophobic core of CCLMs with a maximal 23% drug loading capacity (DLC) and 37% drug loading efficiency (DLE). In vitro DOX release from the CCLMs can be triggered by DTT (10 mM), in contrast to significantly reduced DOX release in the absence of DTT, attesting to the reductively responsive characteristic of the CCLMs. While the CCLMs exhibited minimal cytotoxicity toward HepG2 cancer cells, DOX-loaded CCLMs inhibited the proliferation of the HepG2 cancer cells in a concentration and time dependent manner, suggesting the controlled release of DOX from the DOX-loaded CCLMS in the cellular environment.

Kinetics of ozonation. 4. Reactions of ozone with. cap alpha. -tocopherol and oleate and linoleate esters in carbon tetrachloride and in aqueous micellar solvents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giamalva, D.H.; Church, D.F.; Pryor, W.A.

1986-10-15

Vitamin E (..cap alpha..-tocopherol; ..cap alpha..-T) is known to protect animals against the deleterious effects of ozone in polluted air; one such effect is the ozone-initiated autooxidation of polyunsaturated fatty acids (PUFA) that occur in membranes. In order to assess the possibility of a direct reaction of ozone with ..cap alpha..-T competing with the very fast ozone-PUFA reaction, we have measured the rates of reaction of ozone with ..cap alpha..-T, oleic acid, and linoleic acid. I CCl/sub 4/ as solvent, ..cap alpha..-T reacts with ozone with a rate constant of about 5500 M/sup -1/ s/sup -1/; methyl oleate and methylmore » linoleate react 2 orders of magnitude faster. In aqueous micellar solutions the rate constants for ..cap alpha..-T and the fatty acids are more similar. The k for the ozone/..cap alpha..-T reaction is about 1 x 10/sup 6/ M/sup -1/ s/sup -1/ at pH 7, but decreases as the solution becomes more acidic; the k's for oleic acid and linoleic acid are ca. 1 x 10/sup 6/ M/sup -1/ s/sup -1/ and exhibit no significant pH dependence. Since the ratio of fatty acids to ..cap alpha..-T in membranes is typically at least 100-1000 to 1, we conclude that the direct reaction of ozone with ..cap alpha..-T is unlikely. Thus, the protection that vitamin E provides to animals breathing ozone-containing air must result from vitamin E acting as a free radical scavenger. We have also detected the ..cap alpha..-tocopheroxyl radical as an intermediate from the reaction of ozone with ..cap alpha..-T both in CCl/sub 4/ and aqueous micelles using electron spin resonance spectroscopy. The authors suggest that the observation of this intermediate is consistent with an initial electron transfer from ..cap alpha..-T to ozone.« less

For Stimul-Responsive Polymers with Enhanced Efficiency in Reservoir Recovery Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles McCormick; Roger Hester

Acrylamide-based hydrophobically modified (HM) polybetaines containing N-butylphenylacrylamide (BPAM) and varying amounts of either sulfobetaine (3-(2-acrylamido-2-methylpropanedimethylammonio)-1-propanesulfonate, AMPDAPS) or carboxybetaine (4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate, AMPDAB) comonomers were synthesized via micellar copolymerization. The terpolymers were characterized via {sup 13}C NMR and UV spectroscopies, classical and dynamic light scattering, and potentiometric titration. The response of aqueous polymer solutions to various external stimuli, including changes in solution pH, electrolyte concentration, and the addition of small molecule surfactants, was investigated using surface tension and rheological measurements. Low charge density terpolymers were found to show greater viscosity enhancement upon the addition of surfactant compared to the high charge densitymore » terpolymers. The addition of sodium dodecyl sulfate (SDS) produced the largest maximum in solution viscosity, while N-dodecyl-N,N,N-trimethylammonium bromide (DTAB), N-dodecyl-N,N-dimethylammonio-1-propanesulfonate (SB3-12), and Triton X-100 tended to show reduced viscosity enhancement. In most cases, the high charge density carboxybetaine terpolymer exhibited diminished solution viscosities upon surfactant addition. In our last report, we discussed solution thermodynamic theory that described changes in polymer coil conformation as a function of solution temperature and polymer molecular weight. These polymers contained no ionic charges. In this report, we expand polymer solution theory to account for the electrostatic interactions present in solutions of charged polymers. Polymers with ionic charges are referred to as polyions or polyelectrolytes.« less

Application of colloidal gas aphron suspensions produced from Sapindus mukorossi for arsenic removal from contaminated soil.

PubMed

Mukhopadhyay, Soumyadeep; Mukherjee, Sumona; Hashim, Mohd Ali; Sen Gupta, Bhaskar

2015-01-01

Colloidal gas aphron dispersions (CGAs) can be described as a system of microbubbles suspended homogenously in a liquid matrix. This work examines the performance of CGAs in comparison to surfactant solutions for washing low levels of arsenic from an iron rich soil. Sodium Dodecyl Sulfate (SDS) and saponin, a biodegradable surfactant, obtained from Sapindus mukorossi or soapnut fruit were used for generating CGAs and solutions for soil washing. Column washing experiments were performed in down-flow and up flow modes at a soil pH of 5 and 6 using varying concentration of SDS and soapnut solutions as well as CGAs. Soapnut CGAs removed more than 70% arsenic while SDS CGAs removed up to 55% arsenic from the soil columns in the soil pH range of 5-6. CGAs and solutions showed comparable performances in all the cases. CGAs were more economical since it contains 35% of air by volume, thereby requiring less surfactant. Micellar solubilization and low pH of soapnut facilitated arsenic desorption from soil column. FT-IR analysis of effluent suggested that soapnut solution did not interact chemically with arsenic thereby facilitating the recovery of soapnut solution by precipitating the arsenic. Damage to soil was minimal arsenic confirmed by metal dissolution from soil surface and SEM micrograph. Copyright © 2014 Elsevier Ltd. All rights reserved.

Self-association properties of 4-[1-hydroxy-1-methylethyl]-2-propyl-1-[4-[2-[tetrazole-5-yl]phenyl]phenyl] methylimidazole-5-carboxylic acid monohydrate (CS-088), an antiglaucoma ophthalmic agent.

PubMed

Kikuchi, Takayuki; Ito, Nobuya; Suzuki, Masahiko; Kusai, Akira; Iseki, Ken; Sasaki, Hitoshi

2005-08-11

Self-association properties of CS-088, an antiglaucoma ophthalmic agent, were investigated. Various analytical methods, such as surface tension measurement, demonstrated that CS-088 is a self-associating compound with critical micellar concentration (CMC) of approximately 10 mg/mL. Light scattering analysis revealed that the micellar molecular weight (MMW) of CS-088 aggregates well above the CMC was approximately 2260, corresponding to a pentamer. In addition, the MMW corresponding to a dimer was detected by NMR spectroscopy, indicating that self-association of monomers to pentamers is via the formation of dimers. According to the Stokes-Einstein equation, hydrodynamic radii of the dimer and pentamer were calculated to be 0.87 and 1.16 nm, respectively. The concentration-dependent change in the NMR chemical shift indicated that hydrophobic interaction between biphenyl groups is an important factor in the self-association of CS-088 molecules. Furthermore, measurement of particle size distribution using a Nicomp Submicron Particle-Sizer revealed that the addition of either n-propanol or urea to CS-088 solution led to monomerization of the dimers and pentamers, suggesting that not only hydrophobic interaction but also hydrogen bonding is involved in stabilizing CS-088 aggregates. No bigger aggregate than a pentamer was formed in the absence of NaCl, whereas further aggregation was observed with increasing concentrations of NaCl.

Mixed micellization between natural and synthetic block copolymers: β-casein and Lutrol F-127.

PubMed

Portnaya, Irina; Khalfin, Rafail; Kesselman, Ellina; Ramon, Ory; Cogan, Uri; Danino, Dganit

2011-02-28

Amphiphilic block copolymers and mixtures of amphiphiles find broad applications in numerous technologies, including pharma, food, cosmetic and detergency. Here we report on the interactions between a biological charged diblock copolymer, β-casein, and a synthetic uncharged triblock copolymer, Lutrol F-127 (EO(101)PO(56)EO(101)), on their mixed micellization characteristics and the micelles' structure and morphology. Isothermal titration calorimetry (ITC) experiments indicate that mixed micelles form when Lutrol is added to monomeric as well as to assembled β-casein. The main driving force for the mixed micellization is the hydrophobic interactions. Above β-casein CMC, strong perturbations caused by penetration of the hydrophobic oxypropylene sections of Lutrol into the protein micellar core lead to disintegration of the micelles and reformation of mixed Lutrol/β-casein micelles. The negative enthalpy of micelle formation (ΔH) and cooperativity increase with raising β-casein concentration in solution. ζ-potential measurements show that Lutrol interacts with the protein micelles to form mixed micelles even below its critical micellization temperature (CMT). They further indicate that Lutrol effectively masks the protein charges, probably by forming a coating layer of the ethyleneoxide rich chains. Small-angle X-ray scattering (SAXS) and cryogenic-transmission electron microscopy (cryo-TEM) indicate relatively small changes in the oblate micellar shape, but do show swelling along the small axis of β-casein micelles in the presence of Lutrol, thereby confirming the formation of mixed micelles.

Spray-dried casein-based micelles as a vehicle for solubilization and controlled delivery of flutamide: formulation, characterization, and in vivo pharmacokinetics.

PubMed

Elzoghby, Ahmed O; Helmy, Maged W; Samy, Wael M; Elgindy, Nazik A

2013-08-01

Novel casein (CAS)-based micelles loaded with the poorly soluble anti-cancer drug, flutamide (FLT), were successfully developed in a powdered form via spray-drying technique. Genipin (GNP) was used to crosslink CAS micelles as demonstrated by color variation of the micelles. Drug solubilization was enhanced by incorporation within the hydrophobic micellar core which was confirmed by solubility study and UV spectra. Spherical core-shell micelles were obtained with a particle size below 100 nm and zeta potential around -30 mV. At low drug loading, FLT was totally incorporated within micellar core as revealed by thermal analysis. However, at higher loading, excess non-incorporated drug at micelle surface caused a significant reduction in the surface charge density. Turbidity measurements demonstrated the high physical stability of micelles for 2 weeks dependent on GNP-crosslinking degree. In a dry powdered form, the micelles were stable for 6 months with no significant changes in drug content or particle size. A sustained drug release from CAS micelles up to 5 days was observed. After i.v. administration into rats, CAS micelles exhibited a prolonged plasma circulation of FLT compared to drug solution. Furthermore, a more prolonged drug systemic circulation was observed for GNP-crosslinked micelles. Overall, this study reports the application of spray-dried natural protein-based micelles for i.v. delivery of hydrophobic anti-cancer drugs such as FLT. Copyright © 2013 Elsevier B.V. All rights reserved.

Development and Validation of a Micellar Capillary Electrophoresis Method for Determination of IFNβ-1b in Lyophilized Formulation of a Biosimilar Product

PubMed Central

Dadgarnejad, Manuchehr; Rastegar, Hosein; Ilka, Hooshmand; Shekarchi, Maryam; Adib, Nooshin; Alebouyeh, Mahmood; Keypour, Nadia; Shoeibi, Shahram; Kobarfard, Farzad; Fazeli, Mohammad Reza

2015-01-01

Human interferons (IFNs) are key cytokines secreted by immune system. They have several effects such as antiviral and anti tumors activity, activating immune cells and healing of multiple sclerosis. The type IFNs present in humans are α ,β and Υ. IFN β is a polypeptide, normally produced by fibroblasts and seems to be more species-specific than IFN. Structural properties of IFNs are important for their biologic effects. There are a few analytical techniques for separation, identification and determination of IFNs in its formulations such as mass spectroscopy, RP-HPLC and capillary electrophoresis (CE). In this study we used Micellar Electrokinetic Chromatography (MEKC) as a unique mode of CE because of its capability to separate neutral as well as charged solutes. We used sodium tetraborate (Borax) as buffer without any modifier and sodium dodecyl sulfate (SDS) as surfactant. The optimum MECK running buffer consisted of Borate 50 Mm; SDS 20 mM pH =9.6. The validated method was used for determination of the IFN β-1b formulation which is manufactured in Iran. From 9 collected different batches, all of them had acceptable potency as claimed on their label with average 102.25 ±10.030 %. This is the first time that a MEKC method is introduced for quantification of IFN β-1b in its pharmaceutical dosage forms. The method is reliable safe, rapid and accurate. PMID:26330863

Development and Validation of a Micellar Capillary Electrophoresis Method for Determination of IFNβ-1b in Lyophilized Formulation of a Biosimilar Product.

PubMed

Dadgarnejad, Manuchehr; Rastegar, Hosein; Ilka, Hooshmand; Shekarchi, Maryam; Adib, Nooshin; Alebouyeh, Mahmood; Keypour, Nadia; Shoeibi, Shahram; Kobarfard, Farzad; Fazeli, Mohammad Reza

2015-01-01

Human interferons (IFNs) are key cytokines secreted by immune system. They have several effects such as antiviral and anti tumors activity, activating immune cells and healing of multiple sclerosis. The type IFNs present in humans are α ,β and Υ. IFN β is a polypeptide, normally produced by fibroblasts and seems to be more species-specific than IFN. Structural properties of IFNs are important for their biologic effects. There are a few analytical techniques for separation, identification and determination of IFNs in its formulations such as mass spectroscopy, RP-HPLC and capillary electrophoresis (CE). In this study we used Micellar Electrokinetic Chromatography (MEKC) as a unique mode of CE because of its capability to separate neutral as well as charged solutes. We used sodium tetraborate (Borax) as buffer without any modifier and sodium dodecyl sulfate (SDS) as surfactant. The optimum MECK running buffer consisted of Borate 50 Mm; SDS 20 mM pH =9.6. The validated method was used for determination of the IFN β-1b formulation which is manufactured in Iran. From 9 collected different batches, all of them had acceptable potency as claimed on their label with average 102.25 ±10.030 %. This is the first time that a MEKC method is introduced for quantification of IFN β-1b in its pharmaceutical dosage forms. The method is reliable safe, rapid and accurate.

Differential thermodynamic signature of carbon nanomaterials using amphiphilic micellar probe

NASA Astrophysics Data System (ADS)

Bhattacharyya, Tamoghna; Dasgupta, Anjan Kr

2018-04-01

The thermodynamic signature of single-wall carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (rG-O) using amphiphilic micellar probe has been explored. The study reveals an intricate correlation between nano-surface topology and calorimetric profile of SWCNTs, MWCNTs and rG-O. The critical micelle concentration (CMC) is found to be sensitive to the topological diversity of nanomaterials. The study explores a thermodynamic approach to characterize the nano-surface topology of SWCNTs, MWCNTs and graphene surface.

Comments on some novel approaches for the determination of micellar aggregation numbers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kratohvil, J.P.

1980-05-01

Micellar aggregation numbers of sodium dodecyl sulfates in water and at several concentrations of soidum chloride from several recent papers and from earlier literature have been critically evaluated. The data of D.A. Doughty (J. Phys. Chem. 83, 2621, 1979) based on sedimentation equilibrium and H.F. Huisman (Proc. Kon. Ned. Akad. Wetensch. B 67, 367, 376, 388, 407, 1964) from intensity light scattering are recommended as standared reference data for sodium dodecyl sulfate. 37 references.

Fabrication of Two-Dimensional Arrays of Diameter-Tunable PS-b-P2VP Nanowires at the Air/Water Interface.

PubMed

Zhao, Xingjuan; Yu, Xiaoli; Lee, Yong-Ill; Liu, Hong-Guo

2016-11-15

Composite thin films with well-defined and parallel nanowires were fabricated from the binary blends of a diblock copolymer polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) and several homopolystyrenes (h-PSs) at the air/liquid interface through a facile technique, which involves solution self-assembly, interface adsorption, and further self-organization processes. It was confirmed that the nanowires that appeared at the air/water interface came from the cylindrical micelles formed in solution. Interestingly, the diameters of the nanowires are uniform and can be tuned precisely from 45 to 247 nm by incorporating the h-PS molecules into the micellar core. This parallel alignment of the nanowires has potential applications in optical devices and enables the nanowires to be used as templates to prepare functional nanostructures. The extent to which h-PS molecules with different molecular weights are able to influence the diameter control of the nanowires was also systematically investigated.

Nafion as Cosurfactant: Solubilization of Nafion in Water in the Presence of Pluronics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelarakis, Antonios; Giannelis, Emmanuel P.

2011-01-18

Incorporation of Nafion to aqueous solutions of Pluronics adversely impacts micellization due to extensive Nafion/copolymer interactions. Light scattering and zeta potential measurements provide evidence for the formation of sizable and stable Nafion/copolymer complexes, in expense of the neat copolymer micelles. At high copolymer concentrations, the overall interaction diagram of Nafion/copolymer reflects the competitive action of the release of packing constraints due to micellar destabilization induced by Nafion on one hand and the gelator nature of the Nafion on the other. Measurements using a quartz crystal microbalance (QCM-D) show that aqueous solutions of Pluronics (even at very low concentration) can dissolvemore » the Nafion coating on the crystal resonator, while typical low molecular weight ionic surfactants fail to induce similar effects. These studies demonstrate that complexation with this class of copolymers is a facile route to impart dispersibility to Nafion in aqueous environments that otherwise can be achieved through tedious and harsh treatments.« less

Kinetic control of block copolymer self-assembly into multicompartment and novel geometry nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Yingchao; Wang, Xiaojun; Zhang, Ke; Wooley, Karen; Mays, Jimmy; Percec, Virgil; Pochan, Darrin

2012-02-01

Micelles with the segregation of hydrophobic blocks trapped in the same nanoparticle core have been produced through co-self-assembly of two block copolymers in THF/water dilute solution. The dissolution of two block copolymer sharing the same polyacrylic acid PAA blocks in THF undergoes consequent aggregation and phase separation through either slow water titration or quick water addition that triggers the micellar formation. The combination and comparison of the two water addition kinetic pathways are the keys of forming multicompartment structures at high water content. Importantly, the addition of organic diamine provides for acid-base complexation with the PAA side chains which, in turn, plays the key role of trapping unlike hydrophobic blocks from different block copolymers into one nanoparticle core. The kinetic control of solution assembly can be applied to other molecular systems such as dendrimers as well as other block copolymer molecules. Transmission electron microscopy, cryogenic transmission electron microscopy, light scattering have been applied to characterize the micelle structures.

Stability conditions and mechanism of cream soaps: role of glycerol.

PubMed

Sagitani, Hiromichi

2014-01-01

Fatty acids, fatty acid potassium soaps, glycerol and water are essential ingredients in the production of stable cream soaps. In this study, the behavior of these components in solution was investigated to elucidate the stability conditions and mechanism of cream soaps. It was determined that the cream soaps were a dispersion of 1:1 acid soap (1:1 molar ratio of potassium soap/fatty acid) crystals in the lamellar gel phase, which has confirmed from the phase behavior diagrams and small angle X-ray scattering data. Glycerol was crucial ingredient in the formation of the lamellar gel phase. The cleansing process of the cream soaps was also evaluated using the same diagrams. The structure of the continuous phase in cream soaps changed from lamellar gel to a micellar aqueous solution upon the addition of water. This structural change during the washing process is important in producing the foaming activity of acid soaps to wash away dirt or excess fats from the skin surface.

Development of a Coarse-grained Model of Polypeptoids for Studying Self-assembly in Solution

NASA Astrophysics Data System (ADS)

Du, Pu; Rick, Steven; Kumar, Revati

Polypeptoid, a class of highly tunable biomimetic analogues of peptides, are used as a prototypical model system to study self-assembly. The focus of this work is to glean insight into the effect of electrostatic and other non-covalent secondary interactions on the self-assembly of sequence-defined polypeptoids, with different charged and uncharged side groups, in solution that will complement experiments. Atomistic (AA) molecular dynamics simulation can provide a complete description of self-assembly of polypeptoid systems. However, the long simulation length and time scales needed for these processes require the development of a computationally cheaper alternative, namely coarse-grained (CG) models. A CG model for studying polypeptoid micellar interactions is being developed, parameterized on atomistic simulations, using a hybridized approach involving the OPLS-UA force filed and the Stillinger-Weber (SW) potential form. The development of the model as well as the results from the simulations on the self-assembly as function of polypeptoid chemical structure and sequences will be presented.

Unlocking Chain Exchange in Highly Amphiphilic Block Polymer Micellar Systems: Influence of Agitation.

PubMed

Murphy, Ryan P; Kelley, Elizabeth G; Rogers, Simon A; Sullivan, Millicent O; Epps, Thomas H

2014-11-18

Chain exchange between block polymer micelles in highly selective solvents, such as water, is well-known to be arrested under quiescent conditions, yet this work demonstrates that simple agitation methods can induce rapid chain exchange in these solvents. Aqueous solutions containing either pure poly(butadiene- b -ethylene oxide) or pure poly(butadiene- b -ethylene oxide- d 4 ) micelles were combined and then subjected to agitation by vortex mixing, concentric cylinder Couette flow, or nitrogen gas sparging. Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering. Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours. The linear kinetics with respect to agitation time suggested a surface-limited exchange process at the air-water interface. These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies.

Micellar modified spectrophotometric determination of nitrobenzenes based upon reduction with tin(II), diazotisation and coupling with the Bratton-Marshall reagent.

PubMed

Escrig-Tena, I; Alvarez Rodríguez, L; Esteve-Romero, J; García-Alvarez-Coque, M C

1998-09-01

Nitrobenzenes, such as the antibiotic chloramphenicol, the vasodilator nicardipine, and the herbicides dinitramin, dinobuton, fenitrothion, methylparathion, oxyfluorfen, parathion, pendimethalin, quintozene, and trifluralin, were determined by using a spectrophotometric method in the visible region (540 nm). The method was based on the reduction of the nitrobenzenes to arylamines with tin(II) chloride, diazotisation of the arylamines and coupling of the diazonium ions with the Bratton-Marshall reagent. The two latter reactions were performed in a micellar medium of sodium dodecyl sulphate. The linear calibration range was 2x10(-6) to 7x10(-5) M (r>0.999), with limits of detection in the 10(-7) M level, which is 2-6 fold lower with respect to the corresponding spectrophotometric procedure in non-micellar medium. The procedure was applied to the analysis of the compounds in commercial preparations (pharmaceuticals and herbicide formulations) and in water samples, with good recoveries.

Responsive micellar films of amphiphilic block copolymer micelles: control on micelle opening and closing.

PubMed

Chen, Zhiquan; He, Changcheng; Li, Fengbin; Tong, Ling; Liao, Xingzhi; Wang, Yong

2010-06-01

We reported the deliberate control on the micelle opening and closing of amphiphilic polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) micellar films by exposing them to selective solvents. We first treated the micellar films with polar solvents including ethanol and water (pH = 4, 8, and 12) that have different affinities to P2VP. We observed opening of the micelles in all the cases. Both the size of opened pores and the opening rate are dependent on the solvency of different solvents for P2VP. We then explored the closing behavior of the opened micelles using solvents having different affinities to PS. We found that the opened micelles were recovered to their initial closed micelle forms. The recovery was accompanied by a slow micelle disassociation process which gradually reduced the micelle size. The rates of the micelle closing and disassociation are also dependent on the solvency of different solvents for PS.

Chiral separation of amino acids in biological fluids by micellar electrokinetic chromatography with laser-induced fluorescence detection.

PubMed

Thorsén, G; Bergquist, J

2000-08-18

A method is presented for the chiral analysis of amino acids in biological fluids using micellar electrokinetic chromatography (MEKC) and laser-induced fluorescence (LIF). The amino acids are derivatized with the chiral reagent (+/-)-1-(9-anthryl)-2-propyl chloroformate (APOC) and separated using a mixed micellar separation system. No tedious pre-purification of samples is required. The excellent separation efficiency and good detection capabilities of the MEKC-LIF system are exemplified in the analysis of urine and cerebrospinal fluid. This is the first time MEKC has been reported for chiral analysis of amino acids in biological fluids. The amino acids D-alanine, D-glutamine, and D-aspartic acid have been observed in cerebrospinal fluid, and D-alanine and D-glutamic acid in urine. To the best of our knowledge no measurements of either D-alanine in cerebrospinal fluid or D-glutamic acid in urine have been presented in the literature before.

Mechanistic Analysis of Cocrystal Dissolution as a Function of pH and Micellar Solubilization

PubMed Central

2016-01-01

The purpose of this work is to provide a mechanistic understanding of the dissolution behavior of cocrystals under the influence of ionization and micellar solubilization. Mass transport models were developed by applying Fick’s law of diffusion to dissolution with simultaneous chemical reactions in the hydrodynamic boundary layer adjacent to the dissolving cocrystal surface to predict the pH at the dissolving solid–liquid interface (i.e., interfacial pH) and the flux of cocrystals. To evaluate the predictive power of these models, dissolution studies of carbamazepine–saccharin (CBZ-SAC) and carbamazepine–salicylic acid (CBZ-SLC) cocrystals were performed at varied pH and surfactant concentrations above the critical stabilization concentration (CSC), where the cocrystals were thermodynamically stable. The findings in this work demonstrate that the pH dependent dissolution behavior of cocrystals with ionizable components is dependent on interfacial pH. This mass transport analysis demonstrates the importance of pH, cocrystal solubility, diffusivity, and micellar solubilization on the dissolution rates of cocrystals. PMID:26877267

Mechanistic Analysis of Cocrystal Dissolution as a Function of pH and Micellar Solubilization.

PubMed

Cao, Fengjuan; Amidon, Gordon L; Rodriguez-Hornedo, Nair; Amidon, Gregory E

2016-03-07

The purpose of this work is to provide a mechanistic understanding of the dissolution behavior of cocrystals under the influence of ionization and micellar solubilization. Mass transport models were developed by applying Fick's law of diffusion to dissolution with simultaneous chemical reactions in the hydrodynamic boundary layer adjacent to the dissolving cocrystal surface to predict the pH at the dissolving solid-liquid interface (i.e., interfacial pH) and the flux of cocrystals. To evaluate the predictive power of these models, dissolution studies of carbamazepine-saccharin (CBZ-SAC) and carbamazepine-salicylic acid (CBZ-SLC) cocrystals were performed at varied pH and surfactant concentrations above the critical stabilization concentration (CSC), where the cocrystals were thermodynamically stable. The findings in this work demonstrate that the pH dependent dissolution behavior of cocrystals with ionizable components is dependent on interfacial pH. This mass transport analysis demonstrates the importance of pH, cocrystal solubility, diffusivity, and micellar solubilization on the dissolution rates of cocrystals.

Stability of a secondary-type recovery process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.

1970-04-21

To provide good mobility control and to protect the components of the micellar dispersion displacing fluid from ''leaching'' into the drive fluid (water), the front portion of the drive fluid contained a mobility reducing agent, an electrolyte, and a semipolar organic compound. Berea sandstone cores (20.2 percent porosity, 336 md permeability) were saturated with water from Henry lease in Illinois (18,000 ppM TDS), flooded with sweet black crude oil (7 cp at 72/sup 0/F) from the Henry lease, and waterflooded with Henry lease water. A recovery of 93.9 percent of original oil in place was obtained by a micellar dispersionmore » followed by the mobility buffer. The micellar dispersion contained ammonium petroleum sulfonate, crude column overhead (a heavy naptha), isopropanol, p-nonyl phenol, water and sodium hydroxide. No. 530 Pusher, water from the Palestine water reservoir in Palestine, Illinois (450 ppM TDS), 50 ppM ammonium thiocyanate, n-butanol, and isopropyl alcohol (to facilitate the solubilization of the polymer) were in the mobility buffer.« less

Stability of a secondary-type recovery process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.

1970-07-14

To provide good mobility control and to protect the components of the micellar dispersion displacing fluid from ''leaching'' into the drive fluid (water), the front portion of the drive fluid contained a mobility reducing agent, an electrolyte, and a semipolar organic compound. Berea sandstone cores (20.2 percent porosity, 336 md permeability) were saturated with water from Henry lease in Illinois (18,000 ppM TDS), flooded with sweet black crude oil (7 cp at 72/sup 0/F) from the Henry lease, and waterflooded with Henry lease water. A recovery of 93.9 percent of original oil in place was obtained by a micellar dispersionmore » followed by the mobility buffer. The micellar dispersion contained ammonium petroleum sulfonate, crude column overhead (a heavy naptha), isopropanol, p-nonyl phenol, water and sodium hydroxide. No. 530 Pusher, water from the Palestine water reservoir in Palestine, Illinois (450 ppM TDS), 50 ppM ammonium thiocyanate, n-butanol, and isopropyl alcohol (to facilitate the solubilization of the polymer) were in the mobility buffer.« less

Micellar Electrolytes in Organic Electrochemical Transistors

NASA Astrophysics Data System (ADS)

Cicoira, Fabio; Giuseppe, Tarabella; Nanda, Gaurav; Iannotta, Salvatore; Santato, Clara

2012-02-01

Organic electrochemical transistors (OECTs) are promising for applications in sensing and bioelectronics. OECTs consist of a conducting polymer film (transistor channel) in contact with an electrolyte. A gate electrode immersed in the electrolyte controls the doping/dedoping level of the conducting polymer. OECTs can be operated in aqueous electrolytes, making possible the implementation of organic electronic materials at the interface with biology. The inherent signal amplification of OECTs has the potential to yield sensors with low detection limits and high sensitivity. In this talk we will present recent studies on OECTs using ionic surfactants (such as hexadecyl-trimethyl-ammonium bromide) as electrolytes. As the conducting polymer we used PEDOT:PSS, i.e. (Poly,3-4 ethylenedioxythiopene) doped with Poly(styrene sulphonate). Interestingly, ionic surfactant electrolytes result in large transistor current modulation, especially beyond the critical micellar concentration (CMC). Since micelles play a primary role in biological processes and drug-delivery systems, the use for micellar electrolytes opens new exciting opportunities for the use of OECTs in bioelectronics.

Comparative Study of Different Nano-Formulations of Curcumin for Reversal of Doxorubicin Resistance in K562R Cells.

PubMed

Dash, Tapan K; Konkimalla, V Badireenath

2017-02-01

Curcumin is very well established as a chemo-therapeutic, chemo-preventive and chemo-sensitizing agent in diverse disease conditions. As the isolated pure form has poor solubility and pharmacokinetic problems, therefore it is encapsulated in to several nano-formulations to improve its bioavailability. Here in the current study, we aim to compare different nano-formulations of curcumin for their chemo-sensitizing activity in doxorubicin (DOX) resistant K562 cells. Four different curcumin formulations were prepared namely DMSO assisted curcumin nano-dispersion (CurD, 260 nm), liposomal curcumin (CurL, 165 nm), MPEG-PCL micellar curcumin (CurM, 18 nm) and cyclodextrin encapsulated curcumin (CurN, 37 nm). The formulations were subjected to particle characterizations (size, zeta potential, release studies), followed by biological assays such as cellular uptake, P-gp inhibitory activity and reversal of DOX resistance by co-treatment with DOX. Curcumin uptake in K562N and K562R cells was mildly reduced when treated with CurL and CurM, while for CurD and CurN the uptake remained equivalent. However, CurL retained P-gp inhibitory activity of curcumin and with a considerable chemo-sensitizing effect but CurM showed no P-gp inhibitory activity. CurN retained above biological activities, but requires a secondary carrier under in vivo conditions. From the results, CurM was found to be most suitable for solubilization of curcumin where as CurL can be considered as most suitable nano-formulation for reversal of DOX resistance.

Hierarchical structure and dynamics of oligocarbonate-functionalized PEG block copolymer gels

NASA Astrophysics Data System (ADS)

Prabhu, Vivek; Wei, Guangmin; Ali, Samim; Venkataraman, Shrinivas; Yang, Yi Yan; Hedrick, James

Hierarchical, self-assembled block copolymers in aqueous solutions provide advanced materials for biomaterial applications. Recent advancements in the synthesis of aliphatic polycarbonates have shown nontraditional micellar and hierarchical structures driven by the supramolecular assembly of the carbonate block functionality that includes cholesterol, vitamin D, and fluorene. This presentation shall describe the supramolecular assembly structure and dynamics observed by static and dynamic light scattering, small-angle neutron scattering and transmission electron microscopy in a model pi-pi stacking driven fluorene system. The combination of real-space and reciprocal space methods to develop appropriate models that quantify the structure from the micelle to transient gel network will be discussed. 1) Biomedical Research Council, Agency for Science, Technology and Research, Singapore, 2) NIST Materials Genome Initiative.

Conductive cotton prepared by polyaniline in situ polymerization using laccase.

PubMed

Zhang, Ya; Dong, Aixue; Wang, Qiang; Fan, Xuerong; Cavaco-Paulo, Artur; Zhang, Ying

2014-09-01

The high-redox-potential catalyst laccase, isolated from Aspergillus, was first used as a biocatalyst in the oxidative polymerization of water-soluble conductive polyaniline, and then conductive cotton was prepared by in situ polymerization under the same conditions. The polymerization of aniline was performed in a water dispersion of sodium dodecylbenzenesulfonate (SDBS) micellar solution with atmospheric oxygen serving as the oxidizing agent. This method is ecologically clean and permits a greater degree of control over the kinetics of the reaction. The conditions for polyaniline synthesis were optimized. Characterizations of the conducting polyaniline and cotton were carried out using Fourier transform infrared spectroscopy, UV-vis spectroscopy, cyclic voltammetry, the fabric induction electrostatic tester, and the far-field EMC shielding effectiveness test fixture.

Optical Spectroscopy and Photophysics of Single Wall Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Brus, Louis

2006-03-01

We explore the fundamental nature and dynamics of excited electronic states in SWNT. Psec luminescence and photobleaching dynamics of SWNTs in micellar solution show that non-radiative Auger recombination is extremely fast. At low pH, nanotube surface endoperoxides protonate and introduce holes that quench the luminescence. At higher concentration these holes also bleach the band gap optical absorption. Near infrared two photon luminescence excitation spectra quantitatively reveal the importance of excitons. In order to characterize excited states in both metallic and semiconducting SWNTs at the single-tube level, we detect white-light Rayleigh scattering from individual tubes suspended over an open slit in a substrate. Diagnostic spectra with high signal to noise are obtained in just a few minutes.

Sampling solution traces for the problem of sorting permutations by signed reversals

PubMed Central

2012-01-01

Background Traditional algorithms to solve the problem of sorting by signed reversals output just one optimal solution while the space of all optimal solutions can be huge. A so-called trace represents a group of solutions which share the same set of reversals that must be applied to sort the original permutation following a partial ordering. By using traces, we therefore can represent the set of optimal solutions in a more compact way. Algorithms for enumerating the complete set of traces of solutions were developed. However, due to their exponential complexity, their practical use is limited to small permutations. A partial enumeration of traces is a sampling of the complete set of traces and can be an alternative for the study of distinct evolutionary scenarios of big permutations. Ideally, the sampling should be done uniformly from the space of all optimal solutions. This is however conjectured to be ♯P-complete. Results We propose and evaluate three algorithms for producing a sampling of the complete set of traces that instead can be shown in practice to preserve some of the characteristics of the space of all solutions. The first algorithm (RA) performs the construction of traces through a random selection of reversals on the list of optimal 1-sequences. The second algorithm (DFALT) consists in a slight modification of an algorithm that performs the complete enumeration of traces. Finally, the third algorithm (SWA) is based on a sliding window strategy to improve the enumeration of traces. All proposed algorithms were able to enumerate traces for permutations with up to 200 elements. Conclusions We analysed the distribution of the enumerated traces with respect to their height and average reversal length. Various works indicate that the reversal length can be an important aspect in genome rearrangements. The algorithms RA and SWA show a tendency to lose traces with high average reversal length. Such traces are however rare, and qualitatively our results show that, for testable-sized permutations, the algorithms DFALT and SWA produce distributions which approximate the reversal length distributions observed with a complete enumeration of the set of traces. PMID:22704580

A novel two-dimensional liquid-chromatography method for online prediction of the toxicity of transformation products of benzophenones after water chlorination.

PubMed

Li, Jian; Ma, Li-Yun; Xu, Li; Shi, Zhi-Guo

2015-08-01

Benzophenone-type UV filters (BPs) are ubiquitous in the environment. Transformation products (TPs) of BPs with suspected toxicity are likely to be produced during disinfection of water by chlorination. To quickly predict the toxicity of TPs, in this study, a novel two-dimensional liquid-chromatography (2D-LC) method was established in which the objective of the first dimension was to separate the multiple components of the BPs sample after chlorination, using a reversed-phase liquid-chromatography mode. A biochromatographic system, i.e. bio-partitioning micellar chromatography with the polyoxyethylene (23) lauryl ether aqueous solution as the mobile phase, served as the second dimension to predict the toxicity of the fraction from the first dimension on the basis of the quantitative retention-activity relationships (QRARs) model. Six BPs, namely 2,4-dihydroxybenzophenone, oxybenzone, 4-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone and 2,2'-dihydroxy-4-methoxybenzophenone, were the target analytes subjected to chlorination. The products of these BPs after chlorination were directly injected to the 2D-LC system for analysis. The results indicated that most TPs may be less toxic than their parent chemicals, but some may be more toxic, and that intestinal toxicity of TPs may be more obvious than blood toxicity. The proposed method is time-saving, high-throughput, and reliable, and has great potential for predicting toxicity or bioactivity of unknown and/or known components in a complex sample. Graphical Abstract The scheme for the 2D-LC online prediction of toxicity of the transformation products of benzophenone-type UV filters after chlorination.

Fluorescent silica nanoparticles containing covalently bound dyes for reporter, marker, and sensor applications

NASA Astrophysics Data System (ADS)

Patonay, Gabor; Henary, Maged; Chapman, Gala; Emer, Kyle; Crow, Sidney

2016-03-01

Silica nanoparticles have proven to be useful in many bioanalytical and medical applications and have been used in numerous applications during the last decade. Combining the properties of silica nanoparticles and fluorescent dyes that may be used as chemical probes or labels can be relatively easy by simply soaking porous silica nanoparticles in a solution of the dye of interest. Under proper conditions the entrapped dye can stay inside the silica nanoparticle for several hours resulting in a useful probe. In spite of the relative durability of these probes, leaching can still occur. A much better approach is to synthesize silica nanoparticles that have the fluorescent dye covalently attached to the backbone structure of the silica nanoparticle. This can be achieved by using appropriately modified tetraethyl orthosilicate (TEOS) analogues during the silica nanoparticle synthesis. The molar ratio of TEOS and modified TEOS will determine the fluorescent dye load in the silica nanoparticle. Dependent on the chemical stability of the reporting dye either reverse micellar (RM) or Stöber method can be used for silica nanoparticle synthesis. If dye stability allows RM procedure is preferred as it results in a much easier control of the silica nanoparticle reaction itself. Also controlling the size and uniformity of the silica nanoparticles are much easier using RM method. Dependent on the functional groups present in the reporting dye used in preparation of the modified TEOS, the silica nanoparticles can be utilized in many applications such as pH sensor, metal ion sensors, labels, etc. In addition surface activated silica nanoparticles with reactive moieties are also excellent reporters or they can be used as bright fluorescent labels. Many different fluorescent dyes can be used to synthesize silica nanoparticles including visible and NIR dyes. Several bioanalytical applications are discussed including studying amoeba phagocytosis.

Enhancement of MHC-I antigen presentation via architectural control of pH-responsive, endosomolytic polymer nanoparticles.

PubMed

Wilson, John T; Postma, Almar; Keller, Salka; Convertine, Anthony J; Moad, Graeme; Rizzardo, Ezio; Meagher, Laurence; Chiefari, John; Stayton, Patrick S

2015-03-01

Protein-based vaccines offer a number of important advantages over organism-based vaccines but generally elicit poor CD8(+) T cell responses. We have previously demonstrated that pH-responsive, endosomolytic polymers can enhance protein antigen delivery to major histocompatibility complex class I (MHC-I) antigen presentation pathways thereby augmenting CD8(+) T cell responses following immunization. Here, we describe a new family of nanocarriers for protein antigen delivery assembled using architecturally distinct pH-responsive polymers. Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize linear, hyperbranched, and core-crosslinked copolymers of 2-(N,N-diethylamino)ethyl methacrylate (DEAEMA) and butyl methacrylate (BMA) that were subsequently chain extended with a hydrophilic N,N-dimethylacrylamide (DMA) segment copolymerized with thiol-reactive pyridyl disulfide (PDS) groups. In aqueous solution, polymer chains assembled into 25 nm micellar nanoparticles and enabled efficient and reducible conjugation of a thiolated protein antigen, ovalbumin. Polymers demonstrated pH-dependent membrane-destabilizing activity in an erythrocyte lysis assay, with the hyperbranched and cross-linked polymer architectures exhibiting significantly higher hemolysis at pH ≤ 7.0 than the linear diblock. Antigen delivery with the hyperbranched and cross-linked polymer architecture enhanced in vitro MHC-I antigen presentation relative to free antigen, whereas the linear construct did not have a discernible effect. The hyperbranched system elicited a four- to fivefold increase in MHC-I presentation relative to the cross-linked architecture, demonstrating the superior capacity of the hyperbranched architecture in enhancing MHC-I presentation. This work demonstrates that the architecture of pH-responsive, endosomolytic polymers can have dramatic effects on intracellular antigen delivery, and offers a promising strategy for enhancing CD8(+) T cell responses to protein-based vaccines.

Compatibility Study of Nanofiltration and Reverse Osmosis Membranes with 1 Cyclohexylpiperidenium Bicarbonate Solutions

DOE Data Explorer

Adhikari, Birendra; Jones, Michael G.; Orme, Christopher J.; Wendt, Daniel S.; Wilson, Aaron D.

2015-10-01

The switchable polarity solvent forward osmosis (SPS FO) desalination process requires use of a polishing filtration step to remove trace quantities of draw solution from the product water stream. Selected nanofiltration (NF) and reverse osmosis (RO) membranes were tested for their ability to recover water from 1-cyclohexylpiperidenium bicarbonate solutions in this application. This submission includes the experimental data used to calculate NF and RO membrane flux-normalized net driving pressure (FNNDP) and flux-normalized rejection (FNR) performance in recovering water from 1-cyclohexylpiperidenium bicarbonate solutions. This data is further described and visualized in the manuscript entitled "Compatibility study of nanofiltration and reverse osmosis membranes with 1 cyclohexylpiperidenium bicarbonate solutions" (see attached Compatibility Study Manuscript).

Micellar Electrokinetic Chromatography of Aminoglycosides.

PubMed

Holzgrabe, Ulrike; Schmitt, Stefanie; Wienen, Frank

2016-01-01

The components of the aminoglycosides, e.g., gentamicin, sisomicin, netilmicin, kanamycin, amikacin, and tobramycin, and related impurities of these antibiotics can be separated by means of micellar electrokinetic chromatography (MEKC). Derivatization with o-phthaldialdehyde and thioglycolic acid is found to be appropriate for these antibiotics. The background electrolyte was composed of sodium tetraborate (100 mM), sodium deoxycholate (20 mM), and β-cyclodextrin (15 mM) having a pH value of 10.0. This method is valid for evaluation of gentamicin, kanamycin, and tobramycin. It has to be adopted for amikacin, paromomycin, neomycin, and netilmicin.

Solubilizing properties of new surface-active agents, products of catalytic oxyethylation of cholic acid.

PubMed

Kołodziejczyk, Michał Krzysztof; Nachajski, Michal Jakub; Lukosek, Marek; Zgoda, Marian Mikołaj

2013-01-01

Solubilizing properties of aqueous solutions of a series of surface-active agents, products of oxyethylation of cholic acid, were examined in the present study. The content of oxyethylated segments determined by means of the 1H NMR method enabled the verification of the molecular mass of surfactants along with the calculation of the structural hydrophilic-lipophilic balance (HLB), the solubility parameter delta1/2, and the required solubility level of balance HLB(R). Viscosimetric measurements enabled the calculation of the limiting viscosity number, the content-average molecular mass, the effective volume, the hydrodynamic radius of the surfactant micelle and their equilibrium adducts with rutin, diclofenac and loratadine (BCS Class II and III). By means of the spectrophotometric method (UV) the amount of the solubilized diclofenac, loratadine and rutin (rutoside) was determined in the equilibrium system (saturated solution) in the environment of aqueous solutions of cholic acid derivatives of n(TE) = 20-70. The obtained results serve as a basis for determining the solubilization mechanism of lipophilic therapeutic products and indirectly for estimating the influence of the above process on pharmaceutical as well as biological availability of a micellar adduct from model drug forms (Lindbladt lithogenolitic index).

Synthesis of cadmium sulfide in situ in reverse micelles and in hydrocarbon gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petit, C.; Pileni, M.P.

1988-04-21

The synthesis in situ of cadmium sulfide semiconductors in AOT reverse micelles produces smaller and more monodispersed particles than are obtained in Triton reverse micelles or in aqueous solution. When gelatine is added to the previous solution, the semiconductor is entrapped in a hydrocarbon gel and it size remains the same as that obtained in reverse micelles. The size of the sulfite cadmium aggregate formed in AOT hydrocarbon gels is similar to that obtained under similar conditions in AOT reverse micelles. AOT surfactant can play the role of stabilizing agent. However, a more efficient stabilization is obtained by adding tomore » AOT reverse micelles another stabilizing agent such as sodium hexametaphosphate. The crystallite size is strongly dependent on the ratio of the cadmium and sulfur ions, defined by x = (Cd/sup 2 +/)/(S/sup 2 -//. The yield of reduced viologen obtained by CdS irradiation in AOT reverse micelles is 15 times more efficient than that formed in aqueous solutions whereas it is only three times more in hydrocarbon gels.« less

Thermodynamics and Structural Evolution during a Reversible Vesicle-Micelle Transition of a Vitamin-Derived Bolaamphiphile Induced by Sodium Cholate.

PubMed

Tian, Jun-Nan; Ge, Bing-Qiang; Shen, Yun-Feng; He, Yu-Xuan; Chen, Zhong-Xiu

2016-03-09

Interaction of endogenous sodium cholate (SC) with dietary amphiphiles would induce structural evolution of the self-assembled aggregates, which inevitably affects the hydrolysis of fat in the gut. Current work mainly focused on the interaction of bile salts with classical double-layered phospholipid vesicles. In this paper, the thermodynamics and structural evolution during the interaction of SC with novel unilamellar vesicles formed from vitamin-derived zwitterionic bolaamphiphile (DDO) were characterized. It was revealed that an increased temperature and the presence of NaCl resulted in narrowed micelle-vesicle coexistence and enlarged the vesicle region. The coexistence of micelles and vesicles mainly came from the interaction of monomeric SC with DDO vesicles, whereas micellar SC contributed to the total solubilization of DDO vesicles. This research may enrich the thermodynamic mechanism behind the structure transition of the microaggregates formed by amphiphiles in the gut. It will also contribute to the design of food formulation and drug delivery system.

Polymer-Based Therapeutics: Nanoassemblies and Nanoparticles for Management of Atherosclerosis

PubMed Central

Lewis, Daniel R.; Kamisoglu, Kubra; York, Adam; Moghe, Prabhas V.

2012-01-01

Coronary arterial disease, one of the leading causes of adult mortality, is triggered by atherosclerosis. A disease with complex etiology, atherosclerosis results from the progressive long-term combination of atherogenesis, the accumulation of modified lipoproteins within blood vessel walls, along with vascular and systemic inflammatory processes. The management of atherosclerosis is challenged by the localized flare-up of several multipronged signaling interactions between activated monocytes, atherogenic macrophages and inflamed or dysfunctional endothelial cells. A new generation of approaches is now emerging founded on multifocal, targeted therapies that seek to reverse or ameliorate the athero-inflammatory cascade within the vascular intima. This article reviews the various classes and primary examples of bioactive configurations of nanoscale assemblies. Of specific interest are polymer-based or polymer-lipid micellar assemblies designed as multimodal receptor-targeted blockers or drug carriers whose activity can be tuned by variations in polymer hydrophobicity, charge, and architecture. Also reviewed are emerging reports on multifunctional nanoassemblies and nanoparticles for improved circulation and enhanced targeting to athero-inflammatory lesions and atherosclerotic plaques. PMID:21523920

Modeling micelle formation and interfacial properties with iSAFT classical density functional theory

NASA Astrophysics Data System (ADS)

Wang, Le; Haghmoradi, Amin; Liu, Jinlu; Xi, Shun; Hirasaki, George J.; Miller, Clarence A.; Chapman, Walter G.

2017-03-01

Surfactants reduce the interfacial tension between phases, making them an important additive in a number of industrial and commercial applications from enhanced oil recovery to personal care products (e.g., shampoo and detergents). To help obtain a better understanding of the dependence of surfactant properties on molecular structure, a classical density functional theory, also known as interfacial statistical associating fluid theory, has been applied to study the effects of surfactant architecture on micelle formation and interfacial properties for model nonionic surfactant/water/oil systems. In this approach, hydrogen bonding is explicitly included. To minimize the free energy, the system minimizes interactions between hydrophobic components and hydrophilic components with water molecules hydrating the surfactant head group. The theory predicts micellar structure, effects of surfactant architecture on critical micelle concentration, aggregation number, and interfacial tension isotherm of surfactant/water systems in qualitative agreement with experimental data. Furthermore, this model is applied to study swollen micelles and reverse swollen micelles that are necessary to understand the formation of a middle-phase microemulsion.

Selection of forward osmosis draw solutes for subsequent integration with anaerobic treatment to facilitate resource recovery from wastewater.

PubMed

Ansari, Ashley J; Hai, Faisal I; Guo, Wenshan; Ngo, Hao H; Price, William E; Nghiem, Long D

2015-09-01

Forward osmosis (FO) can be used to extract clean water and pre-concentrate municipal wastewater to make it amenable to anaerobic treatment. A protocol was developed to assess the suitability of FO draw solutes for pre-concentrating wastewater for potential integration with anaerobic treatment to facilitate resource recovery from wastewater. Draw solutes were evaluated in terms of their ability to induce osmotic pressure, water flux, and reverse solute flux. The compatibility of each draw solute with subsequent anaerobic treatment was assessed by biomethane potential analysis. The effect of each draw solute (at concentrations corresponding to the reverse solute flux at ten-fold pre-concentration of wastewater) on methane production was also evaluated. The results show that ionic organic draw solutes (e.g., sodium acetate) were most suitable for FO application and subsequent anaerobic treatment. On the other hand, the reverse solute flux of inorganic draw solutions could inhibit methane production from FO pre-concentrated wastewater. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Impact of fatty acyl composition and quantity of triglycerides on bioaccessibility of dietary carotenoids.

PubMed

Huo, Tianyao; Ferruzzi, Mario G; Schwartz, Steven J; Failla, Mark L

2007-10-31

A carotenoid-rich salad meal with varying amounts and types of triglycerides (TG) was digested using simulated gastric and small intestinal conditions. Xanthophylls (lutein and zeaxanthin) and carotenes (alpha-carotene, beta-carotene, and lycopene) in chyme and micelle fraction were quantified to determine digestive stability and efficiency of micellarization (bioaccessibility). Micellarization of lutein (+zeaxanthin) exceeded that of alpha- and beta-carotenes, which was greater than that of lycopene for all test conditions. Micellarization of carotenes, but not lutein (+zeaxanthin), was enhanced (P < 0.05) by addition of TG (2.5% v/w) to the meal and was dependent on fatty acyl chain length in structured TG (c18:1 > c8:0 > c4:0). The degree of unsaturation of c18 fatty acyl chains in TG added to the salad purée did not significantly alter the efficiency of micellarization of carotenoids. Relatively low amounts of triolein and canola oil (0.5-1%) were required for maximum micellarization of carotenes, but more oil (approximately 2.5%) was required when TG with medium chain saturated fatty acyl groups (e.g., trioctanoin and coconut oil) was added to the salad. Uptake of lutein and beta-carotene by Caco-2 cells also was examined by exposing cells to micelles generated during the simulated digestion of salad purée with either triolein or trioctanoin. Cell accumulation of beta-carotene was independent of fatty acyl composition of micelles, whereas lutein uptake was slightly, but significantly, increased from samples with digested triolein compared to trioctanoin. The results show that the in vitro transfer of alpha-carotene, beta-carotene, and lycopene from chyme to mixed micelles during digestion requires minimal (0.5-1%) lipid content in the meal and is affected by the length of fatty acyl chains but not the degree of unsaturation in TG. In contrast, fatty acyl chain length has limited if any impact on carotenoid uptake by small intestinal epithelial cells. These data suggest that the amount of TG in a typical meal does not limit the bioaccessibility of carotenoids.

Rapid recovery of dilute copper from a simulated Cu-SDS solution with low-cost steel wool cathode reactor.

PubMed

Chang, Shih-Hsien; Wang, Kai-Sung; Hu, Pei-I; Lui, I-Chun

2009-04-30

Copper-surfactant wastewaters are often encountered in electroplating, printed circuit boards manufacturing, and metal finishing industries, as well as in retentates from micellar-enhanced ultrafiltration process. A low-cost three-dimensional steel wool cathode reactor was evaluated for electrolytic recovery of Cu ion from dilute copper solution (0.2mM) in the presence of sodium dodecyl sulfate (SDS), octylphenol poly (ethyleneglycol) 9.5 ether (TX), nonylphenol poly (oxyethylene) 9 ether (NP9) and polyoxyethylene (20) sorbitan monooleate (TW) and also mixed surfactants (anionic/nonionic). The reactor showed excellent copper recovery ability in comparison to a parallel-plate reactor. The reactor rapidly recovered copper with a reasonable current efficiency. 93% of copper was recovered at current density of 1 A m(-2) and pH 4 in the presence of 8.5mM SDS. Initial solution pH, cathodic current density, solution mixing condition, SDS concentration, and initial copper concentrations significantly influenced copper recovery. The copper recovery rate increased with an increase in aqueous SDS concentrations between 5 and 8.5mM. The influences of nonionic surfactants on Cu recovery from SDS-Cu solution depended not only on the type of surfactants used, but also on applied concentrations. From the copper recovery perspective, TX at 0.1mM or NP should be selected rather than TW, because they did not inhibit copper recovery from SDS-Cu solution.

NBD-labelled phospholipid accelerates apolipoprotein C-II amyloid fibril formation but is not incorporated into mature fibrils

PubMed Central

Ryan, Timothy M.; Griffin, Michael D. W.; Bailey, Michael F.; Schuck, Peter; Howlett, Geoffrey J.

2014-01-01

Human apolipoprotein (apo) C-II is one of several lipid-binding proteins that self-assemble into fibrils and accumulate in disease-related amyloid deposits. A general characteristic of these amyloid deposits is the presence of lipids, known to modulate individual steps in amyloid fibril formation. ApoC-II fibril formation is activated by sub-micellar phospholipids but inhibited by micellar lipids. We examined the mechanism for the activation by sub-micellar lipids using the fluorescently-labelled, short-chain phospholipid, 1-dodecyl-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]-2-hydroxy-glycero-3-phosphocholine (NBD-lyso-12-PC). Addition of submicellar NBD-lyso-12-PC increased the rate of fibril formation by apoC-II approximately two-fold. Stopped flow kinetic analysis using fluorescence detection and low, non-fibril forming concentrations of apoC-II indicated NBD-Lyso-12-PC binds rapidly, in the millisecond timescale, followed by the slower formation of discrete apoC-II tetramers. Sedimentation velocity analysis showed NBD-Lyso-12-PC binds to both apoC-II monomers and tetramers at approximately 5 sites per monomer with an average dissociation constant of approximately 10 μM. Mature apoC-II fibrils formed in the presence of NBD-Lyso-12-PC were devoid of lipid indicating a purely catalytic role for sub-micellar lipids in the activation of apoC-II fibril formation. These studies demonstrate the catalytic potential of small amphiphilic molecules to control protein folding and fibril assembly pathways. PMID:21985034

pH multistage responsive micellar system with charge-switch and PEG layer detachment for co-delivery of paclitaxel and curcumin to synergistically eliminate breast cancer stem cells.

PubMed

Yang, Zhe; Sun, Na; Cheng, Rui; Zhao, Chenyang; Liu, Zerong; Li, Xian; Liu, Jie; Tian, Zhongmin

2017-12-01

Several studies have demonstrated that cancer stem cells (CSCs) are responsible for replenishing bulk tumor cells, generating new tumors and causing metastasis and relapse. Although combination therapy with multiple chemotherapeutics is considered to be a promising approach for simultaneously eliminating non-CSCs and CSCs, it is difficult to deliver drugs into the inner region of a solid tumor where the CSCs are located due to a lack of capillaries. Here, we synthesized a pH-sensitive polymer, poly(ethylene glycol)-benzoic imine-poly(γ-benzyl-l-aspartate)-b-poly(1-vinylimidazole) block copolymer (PPBV), to develop a pH multistage responsive micellar system for co-delivering paclitaxel and curcumin and synergistically eliminating breast cancer stem cells (bCSCs) and non-bCSCs. This pH multistage responsive micellar system could intelligently switch its surface charge from neutral to positive, de-shield its PEG layer and reduce its size after long-circulation and extravasation from leaky blood vessels at tumor sites, thus facilitating their cellular uptake and deep tumor penetration. These advantages were also beneficial for the combinational therapy efficacy of PTX and CUR to reach the maximum level and achieve superior tumor inhibition activity and effective bCSCs-killing capacity in vivo. Consequently, this pH multistage responsive micellar system is a powerful platform for collaborative therapy with PTX and CUR to simultaneously eliminate bCSCs and non-CSCs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Self dispersing mixed micelles forming systems for enhanced dissolution and intestinal permeability of hydrochlorothiazide.

PubMed

Sultan, Amal A; El-Gizawy, Sanaa A; Osman, Mohamed A; El Maghraby, Gamal M

2017-01-01

Mixed micelles provide promising strategy for enhancing dissolution and permeability of drugs. However, their fluid nature limited the stability of the loaded drug and hindered the development of stable oral dosage form. Accordingly, the objective was to develop solid self dispersing mixed micelle forming systems (MMFS) for enhanced dissolution and intestinal permeability of hydrochlorothiazide. Pseudoternary phase diagrams were constructed using sodium cholate, lecithin with either poloxamer 407 or PEG 4000 to determine the composition of MMFS. Both polymer free and poloxamer or PEG containing MMFS were prepared as homogenous matrices or as solid self dispersing powder. The later was developed by adsorption of MMFS on avicel-aerosil mixture. Differential scanning calorimetry provided an evidence for existence of hydrochlorothiazide as molecular dispersion in the MMFS. Dispersing polymer free, PEG 4000 or poloxamer based MMFS in aqueous medium produced micelles having size values of 119, 52.6 and 28nm, respectively. The zeta potential values were -61.8, -59.5 and -19.5mV for the same systems, respectively. Preparation of solid self dispersing MMFS enhanced the dissolution rate of hydrochlorothiazide. The intestinal absorption of hydrochlorothiazide from its aqueous solution and polymer incorporating mixed micellar systems was monitored using in situ rabbit intestinal perfusion technique. The permeability results showed a clear trend for enhanced membrane transport of the drug after being incorporated into poloxamer containing mixed micellar system. The study thus introduced a versatile easily formulated solid self dispersing system with high potential for solving the dissolution and permeability problems of class IV drugs. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation and assessment of carboxylate polyelectrolyte as draw solute for forward osmosis.

PubMed

Cui, Hongtao; Zhang, Hanmin; Jiang, Wei; Yang, Fenglin

2018-02-01

Reverse draw solute diffusion not only reduces the water flux in forward osmosis (FO), but also contaminates the feed solution and eventually increases the regeneration cost of draw solution. In the present study, a new polyelectrolyte was synthesized as FO draw solute to address this problem. Acrylic acid and sodium p-styrenesulfonate monomers with hydrophilic group were used to fabricate carboxylate polyelectrolyte through free radical polymerization reaction. Results demonstrated that the osmotic pressure of carboxylate polyelectrolyte solution had a good linear relationship with concentration, and the viscosity of 0.18 g/mL solution was less than 5.4 cP. Active layer facing draw solution produced the initial water flux of 11.77 LMH and active layer facing feed solution yielded the initial water flux of 6.68 LMH when the concentration of draw solution was 0.18 g/mL. The reverse solute flux was around 1 gMH, and specific reverse solute flux of 0.18 g/mL carboxylate polyelectrolyte draw solution was 0.11 g/L which was much lower than that of traditional inorganic salts. Finally, diluted draw solution was regenerated via ultrafiltration, and the recovery efficiency of 94.78% was achieved. So, carboxylate polyelectrolyte can be suitable draw solute for FO.

Effect of hexadecyltrimethylammonium bromide-based microemulsions on the rate of decomposition of the beta-lactam antibiotic cephaclor.

PubMed

De Oliveira, A G; Scarpa, M V; Chaimovich, H

1997-05-01

Microemulsions of hexadecyltrimethylammonium bromide (HTAB)/n-butanol/hexadecane/water catalyze the intramolecular degradation of cephaclor. The rate increase is a sensitive function of the microemulsion volume fraction and salt concentration. The effects of microemulsions, analyzed quantitatively using a pseudophase ion-exchange model, assumed that the extent of ion dissociation from the microemulsions varies with volume fraction. Comparison of micellar and microemulsion effects on the same reaction shows that microemulsions are less effective catalysts. Acceleration decreased significantly by increasing the relative proportion of n-butanol ratio in microemulsions and by addition of n-butanol in HTAB micelles. Comparison of the activation parameters of the reaction in aqueous solution, microemulsions, and micelles suggests that catalysis by both aggregates is driven mainly by entropic contributions.

Sampling the kinetic pathways of a micelle fusion and fission transition.

PubMed

Pool, René; Bolhuis, Peter G

2007-06-28

The mechanism and kinetics of micellar breakup and fusion in a dilute solution of a model surfactant are investigated by path sampling techniques. Analysis of the path ensemble gives insight in the mechanism of the transition. For larger, less stable micelles the fission/fusion occurs via a clear neck formation, while for smaller micelles the mechanism is more direct. In addition, path analysis yields an appropriate order parameter to evaluate the fusion and fission rate constants using stochastic transition interface sampling. For the small, stable micelle (50 surfactants) the computed fission rate constant is a factor of 10 lower than the fusion rate constant. The procedure opens the way for accurate calculation of free energy and kinetics for, e.g., membrane fusion, and wormlike micelle endcap formation.

Influence of vitamin E acetate and other lipids on the phase behavior of mesophases based on unsaturated monoglycerides.

PubMed

Sagalowicz, L; Guillot, S; Acquistapace, S; Schmitt, B; Maurer, M; Yaghmur, A; de Campo, L; Rouvet, M; Leser, M; Glatter, O

2013-07-02

The phase behavior of the ternary unsaturated monoglycerides (UMG)-DL-α-tocopheryl acetate-water system has been studied. The effects of lipid composition in both bulk and dispersed lyotropic liquid crystalline phases and microemulsions were investigated. In excess water, progressive addition of DL-α-tocopheryl acetate to a binary UMG mixture results in the following phase sequence: reversed bicontinuous cubic phase, reversed hexagonal (H(II)) phase, and a reversed microemulsion. The action of DL-α-tocopheryl acetate is then compared to that of other lipids such as triolein, limonene, tetradecane, and DL-α-tocopherol. The impact of solubilizing these hydrophobic molecules on the UMG-water phase behavior shows some common features. However, the solubilization of certain molecules, like DL-α-tocopherol, leads to the presence of the reversed micellar cubic phase (space group number 227 and symmetry Fd3m) while the solubilization of others does not. These differences in phase behavior are discussed in terms of physical-chemical characteristics of the added lipid molecule and its interaction with UMG and water. From an applications point of view, phase behavior as a function of the solubilized content of guest molecules (lipid additive in our case) is crucial since macroscopic properties such as molecular release depend strongly on the phase present. The effect of two hydrophilic emulsifiers, used to stabilize the aqueous dispersions of UMG, was studied and compared. Those were Pluronic F127, which is the most commonly used stabilizer for these kinds of inverted type structures, and the partially hydrolyzed emulsifier lecithin (Emultop EP), which is a well accepted food-grade emulsifier. The phase behavior of particles stabilized by the partially hydrolyzed lecithin is similar to that of bulk sample at full hydration, but this emulsifier interacts significantly with the internal structure and affects it much more than F127.

Optimisation of resolution in micellar electrokinetic chromatography by multivariate evaluation of electrolytes.

PubMed

Mikaeli, S; Thorsén, G; Karlberg, B

2001-01-12

A novel approach to multivariate evaluation of separation electrolytes for micellar electrokinetic chromatography is presented. An initial screening of the experimental parameters is performed using a Plackett-Burman design. Significant parameters are further evaluated using full factorial designs. The total resolution of the separation is calculated and used as response. The proposed scheme has been applied to the optimisation of the separation of phenols and the chiral separation of (+)-1-(9-anthryl)-2-propyl chloroformate-derivatized amino acids. A total of eight experimental parameters were evaluated and optimal conditions found in less than 48 experiments.

Guest-Release Control in Enzyme-Sensitive, Amphiphilic-Dendrimer-Based Nanoparticles through Photochemical Crosslinking

PubMed Central

Raghupathi, Krishna R.; Azagarsamy, Malar A.; Thayumanavan, S.

2012-01-01

Stimuli sensitive, facially amphiphilic dendrimers have been synthesized and their enzyme-responsive nature has been determined with dual fluorescence responses of both covalently conjugated and non-covalently bound reporter units. These dual responses are correlated to ascertain the effect of enzymatic action on micellar aggregates and the consequential guest release. The release of the guest molecule is conveniently tuned by stabilizing the micellar aggregates through photochemical crosslinking of hydrophobic coumarin units. This photo-crosslinking is also utilized as a tool to investigate the mode of enzyme-substrate interaction in the context of aggregate-monomer equilibrium. PMID:21887830

A new class of draw solutions for minimizing reverse salt flux to improve forward osmosis desalination.

PubMed

Nguyen, Hau Thi; Nguyen, Nguyen Cong; Chen, Shiao-Shing; Ngo, Huu Hao; Guo, Wenshan; Li, Chi-Wang

2015-12-15

The applications of forward osmosis (FO) have been hindered because of the lack of an optimal draw solution. The reverse salt flux from the draw solution not only reduces the water flux but also increases the cost of draw solute replenishment. Therefore, in this study, Tergitol NP7 and NP9 with a long straight carbon chain and low critical micelle concentration (CMC) were coupled with highly charged ethylenediaminetetraacetic acid (EDTA) as an innovative draw solution to minimize reverse salt diffusion in FO for the first time. The results showed that the lowest reverse salt flux of 0.067 GMH was observed when 0.1M EDTA-2Na coupled with 15mM NP7 was used as a draw solution and deionized water was used as a feed solution in FO mode (active layer facing with the feed solution). This is due to the hydrophobic interaction between the tails of NP7 and the FO membrane, thus creating layers on the membrane surface and constricting the FO membrane pores. Moreover, 1M EDTA-2Na coupled with 15mM NP7 is promising as an optimal draw solution for brackish water and sea water desalination. Average water fluxes of 7.68, 6.78, and 5.95 LMH were achieved when brackish water was used as a feed solution (5, 10, and 20g/L NaCl), and an average water flux of 3.81 LMH was achieved when sea water was used as a feed solution (35g/L NaCl). The diluted draw solution was recovered using a nanofiltration (NF-TS80) membrane with a high efficiency of 95% because of the high charge and large size of the draw solution. Copyright © 2015 Elsevier B.V. All rights reserved.

Sodium deoxycholate mediated enhanced solubilization and stability of hydrophobic drug Clozapine in pluronic micelles

NASA Astrophysics Data System (ADS)

Singla, Pankaj; Singh, Onkar; Chabba, Shruti; Aswal, V. K.; Mahajan, Rakesh Kumar

2018-02-01

In this report, the solubilization behaviour of a hydrophobic drug Clozapine (CLZ) in micellar suspensions of pluronics having different hydrophilic lipophilic balance (HLB) ratios viz. P84, F127 and F108 in the absence and presence of bile salt sodium deoxycholate (SDC) has been studied. UV-Vis spectroscopy has been exploited to determine the solubilization capacity of the investigated micellar systems in terms of drug loading efficiency, average number of drug molecules solubilized per micelle (ns), partition coefficient (P) and standard free energy of solubilization (Δ G°). The morphological and structural changes taking place in pluronics in different concentration regimes of SDC and with the addition of drug CLZ has been explored using dynamic light scattering (DLS) and small angle neutron scattering (SANS) measurements. The SANS results revealed that aggregation behaviour of pluronic-SDC mixed micelles gets improved in the presence of drug. The micropolarity measurements have been performed to shed light on the locus of solubilization of the drug in pure and mixed micellar systems. The compatibility between CLZ and drug carriers (pluronics and SDC) was confirmed using powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR) techniques. Among the investigated systems, P84-SDC mixed system was found to be highly efficient for CLZ loading. The long term stability data indicated that CLZ loaded P84-SDC mixed micellar formulation remained stable for 3 months at room temperature. Further, it was revealed that the CLZ loaded P84-SDC mixed micelles are converted into CLZ loaded pure P84 micelles at 30-fold dilutions which remain stable up to 48-fold dilutions. The results from the present studies suggest that P84-SDC mixed micelles can serve as suitable delivery vehicles for hydrophobic drug CLZ.

Prevention of vitamin K deficiency bleeding with three oral mixed micellar phylloquinone doses: results of a 6-year (2005-2011) surveillance in Switzerland.

PubMed

Laubscher, Bernard; Bänziger, Oskar; Schubiger, Gregor

2013-03-01

In 2003, the Swiss guidelines to prevent vitamin K deficiency bleeding (VKDB) were adapted. As two oral doses (2 mg, hour/day 4) of mixed micellar VK preparation had failed to abolish late VKDB, a third dose (week 4) was introduced. This report summarizes the new guidelines acceptance by Swiss pediatricians and the results of a prospective 6-year surveillance to study their influence on the incidence of VKDB. The new guidelines acceptance by Swiss pediatricians was evaluated by a questionnaire sent to all pediatricians of the Swiss Society of Paediatrics. With the help of the Swiss Paediatric Surveillance Unit, the incidence of VKDB was monitored prospectively from July 1, 2005 until June 30, 2011. Over a 6-year period (458,184 live births), there was one case of early and four cases of late VKDB. Overall incidence was 1.09/10(5) (95 % confidence intervals (CI) 0.4-2.6). Late VKDB incidence was 0.87/10(5) (95 % CI 0.24-2.24). All four infants with late VKDB had an undiagnosed cholestasis at the time of bleeding; parents of 3/4 had refused VK prophylaxis, and in 1/4, the third VK dose had been forgotten. Compared with historical control who had received only two oral doses of mixed micellar VK (18 cases for 475,372 live births), the incidence of late VKDB was significantly lower with three oral doses (Chi(2),Yates correction, P = 0.007). VKDB prophylaxis with 3 × 2 mg oral doses of mixed micellar VK seems to prevent adequately infants from VKDB. The main risk factors for VKDB in breast-fed infants are parental VK prophylaxis refusal or an unknown cholestasis.

Folate Receptor Targeted Polymeric Micellar Nanocarriers for Delivery of Orlistat as a Repurposed Drug against Triple Negative Breast Cancer

PubMed Central

Paulmurugan, Ramasamy; Bhethanabotla, Rohith; Mishra, Kaushik; Devulapally, Rammohan; Foygel, Kira; Sekar, Thillai V; Ananta, Jeyarama S; Massoud, Tarik F; Joy, Abraham

2015-01-01

Triple negative breast cancer (TNBC) is a recalcitrant malignancy with no available targeted therapy. Off target effects and poor bioavailability of the FDA approved anti-obesity drug orlistat hinder its clinical translation as a repurposed new drug against TNBC. Here we demonstrate a newly engineered drug formulation for packaging orlistat tailored to TNBC treatment. We synthesized TNBC-specific folate receptor targeted micellar nanoparticles (NPs) carrying orlistat, which improved the solubility (70-80 μg/ml) of this water insoluble drug. The targeted NPs also improved the delivery and bioavailability of orlistat to MDA-MB-231 cells in culture and to tumor xenografts in nude mouse model. We prepared HEA-EHA copolymer micellar NPs by copolymerization of 2-hydroxyethylacrylate (HEA) and 2-ethylhexylacrylate (EHA), and functionalized them with folic acid and an imaging dye. Fluorescence activated cell sorting (FACS) analysis of TNBC cells indicated a dose dependent increase in apoptotic populations in cells treated with free orlistat, orlistat NPs, and folate-receptor targeted Fol-HEA-EHA-orlistat NPs in which Fol-HEA-EHA-orlistat NPs showed significantly higher cytotoxicity than free orlistat. In vitro analysis data demonstrated significant apoptosis at nanomolar concentrations in cells activated through caspase 3 and PARP inhibition. In vivo analysis demonstrated significant antitumor effects in living mice after targeted treatment of tumors, and confirmed by fluorescence imaging. Moreover, Folate receptor targeted Fol-DyLight747-orlistat NPs treated mice exhibited significantly higher reduction in tumor volume compared to control group. Taken together, these results indicate that orlistat packaged in HEA-b-EHA micellar NPs is a highly promising new drug formulation for TNBC therapy. PMID:26553061

Application of Fluorescence Emission for Characterization of Albendazole and Ricobendazole Micellar Systems: Elucidation of the Molecular Mechanism of Drug Solubilization Process.

PubMed

Priotti, Josefina; Leonardi, Darío; Pico, Guillermo; Lamas, María C

2018-04-01

Albendazole (ABZ) and ricobendazole (RBZ) are referred to as class II compounds in the Biopharmaceutical Classification System. These drugs exhibit poor solubility, which profoundly affects their oral bioavailability. Micellar systems are excellent pharmaceutical tools to enhance solubilization and absorption of poorly soluble compounds. Polysorbate 80 (P80), poloxamer 407 (P407), sodium cholate (Na-C), and sodium deoxycholate (Na-DC) have been selected as surfactants to study the solubilization process of these drugs. Fluorescence emission was applied in order to obtain surfactant/fluorophore (S/F) ratio, critical micellar concentration, protection efficiency of micelles, and thermodynamic parameters. Systems were characterized by their size and zeta potential. A blue shift from 350 to 345 nm was observed when ABZ was included in P80, Na-DC, and Na-C micelles, while RBZ showed a slight change in the fluorescence band. P80 showed a significant solubilization capacity: S/F values were 688 for ABZ at pH 4 and 656 for RBZ at pH 6. Additionally, P80 micellar systems presented the smallest size (10 nm) and their size was not affected by pH change. S/F ratio for bile salts was tenfold higher than for the other surfactants. Quenching plots were linear and their constant values (2.17/M for ABZ and 2.29/M for RBZ) decreased with the addition of the surfactants, indicating a protective effect of the micelles. Na-DC showed better protective efficacy for ABZ and RBZ than the other surfactants (constant values 0.54 and 1.57/M, respectively), showing the drug inclusion into the micelles. Entropic parameters were negative in agreement with micelle formation.

A glucose-targeted mixed micellar formulation outperforms Genexol in breast cancer cells.

PubMed

Moretton, Marcela A; Bernabeu, Ezequiel; Grotz, Estefanía; Gonzalez, Lorena; Zubillaga, Marcela; Chiappetta, Diego A

2017-05-01

Breast cancer represents the top cancer among women, accounting 521.000 deaths per year. Development of targeted nanomedicines to breast cancer tissues represents a milestone to reduce chemotherapy side effects. Taking advantage of the over-expression of glucose (Glu) membrane transporters in breast cancer cells, we aim to expand the potential of a paclitaxel (PTX)-loaded mixed micellar formulation based on polyvinyl caprolactam-polyvinylacetate-polyethylene glycol graft copolymer (Soluplus®) and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) by its surface decoration with Glu moieties. The glycopolymer (Soluplus(Glu)) was obtained by microwave-assisted ring opening reaction of δ-gluconolactone initiated by Soluplus®. The glycosylation was confirmed by 1 H NMR and by agglutination assays employing Concanavalin A. The hydrodynamic diameter of Soluplus(Glu) micelles was characterized by dynamic light scattering (100.3±3.8nm) as well as the critical micellar concentration value (0.0151% w/v). Then, a mixed micelle formulation employing Soluplus®, Soluplus(Glu) and TPGS (3:1:1wt ratio) loaded with PTX (4mg/mL) was developed as a multifunctional nanocarrier. Its in vitro anticancer performance in MCF-7 (1.6-fold) and MDA-MB-231 (14.1-fold) was significantly enhanced (p<0.05) versus the unique commercially available micellar-based PTX-nanoformulation (Genexol®). Furthermore, the in vitro PTX cellular uptake assays revealed that the drug intracellular/cell content was significantly (p<0.05) higher for the Glu-containing mixed micelles versus Genexol® after 6h of incubation with MCF-7 (30.5-fold) and MDA-MB-231 (5-fold). Overall, results confirmed the potential of our Glu-decorated mixed colloidal formulation as an intelligent nanocarrier for PTX-targeted breast cancer chemotherapy. Copyright © 2017 Elsevier B.V. All rights reserved.

Development and validation of a micellar electrokinetic chromatography method for quantitative determination of butenolides in Piper malacophyllum (C. Presl) C. DC.

PubMed

de Oliveira, Alberto; Silva, Claudinei A; Silva, Adalberto M; Tavares, Marina F M; Kato, Massuo J

2010-01-01

A large number of natural and synthetic compounds having butenolides as a core unit have been described and many of them display a wide range of biological activities. Butenolides from P. malacophyllum have presented potential antifungal activities but no specific, fast, and precise method has been developed for their determination. To develop a methodology based on micellar electrokinetic chromatography to determine butenolides in Piper species. The extracts were analysed in an uncoated fused-silica capillaries and for the micellar system 20 mmol/L SDS, 20% (v/v) acetonitrile (ACN) and 10 mmol/L STB aqueous buffer at pH 9.2 were used. The method was validated for precision, linearity, limit of detection (LOD) and limit of quantitation (LOQ) and the standard deviations were determined from the standard errors estimated by the regression line. A micellar electrokinetic chromatography (MEKC) method for determination of butenolides in extracts gave full resolution for 1 and 2. The analytical curve in the range 10.0-50.0 µg/mL (r(2) = 0.999) provided LOD and LOQ for 1 and 2 of 2.1/6.3 and 1.1/3.5 µg/mL, respectively. The RSD for migration times were 0.12 and 1.0% for peak area ratios with 100.0 ± 1.4% of recovery. A novel high-performance MEKC method developed for the analysis of butenolides 1 and 2 in leaf extracts of P. malacophyllum allowed their quantitative determined within an analysis time shorter than 5 min and the results indicated CE to be a feasible analytical technique for the quantitative determination of butenolides in Piper extracts. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of polymers on the rotational viscosities of nematic liquid crystals and dynamics of field alignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, D.

Many of the important physical phenomena exhibited by the nematic phase, such as its unusual flow properties and its responses to the electric and the magnetic fields, can be discussed regarding it as a continous medium. The Leslie-Erickson dynamic theory has the six dissipative coefficients from continuum model of liquid crystal. Parodi showed that only five of them are independent, when Onsagar`s reciprocal relations are used. One of these, which has no counterpart in the isotropic liquids, is the rotational viscosity co-efficient, {gamma}{sub 1}. The main objective of this project is to study the rotational viscosities of selected micellar nematicmore » systems and the effect of dissolved polymers in micellar and thermotropic liqud crystals. We used rotating magnetic field method which allows one to determine {gamma}{sub 1} and the anisotropic magnetic susceptibility, {chi}{sub a}. For the ionic surfactant liquid crystals of SDS and KL systems used in this study, the rotational viscosity exhibited an extraordinary drop after reaching the highest values {gamma}{sub 1} as the temperature was lowered. This behavior is not observed in normal liquid crystals. But this phenomena can be attributed to the existence of nematic biaxial phase below the rod-like nematic N{sub c} phase. The pretransitional increase in {gamma}{sub 1} near the disk-like nematic to smectic-A phase transition of the pure CsPFO/H{sub 2}O systems are better understood with the help of mean-field models of W.L. McMillan. He predicted a critical exponent {nu} = {1/2} for the divergence of {gamma}{sub 1}. The polymer (PEO, molecular weight = 10{sup 5}) dissolved in CsPFO/H{sub 2}O system (which has 0.6% critical polymer concentration), suppressed the nematic to lamellar smectic phase transition in concentrated polymer solutions (0.75% and higher). In dilute polymer solutions with lower than 0.3% polyethylene-oxide, a linear increase of {gamma}{sub 1} is observed, which agrees with Brochard theory.« less

Galantamine-loaded PLGA nanoparticles, from nano-emulsion templating, as novel advanced drug delivery systems to treat neurodegenerative diseases

NASA Astrophysics Data System (ADS)

Fornaguera, C.; Feiner-Gracia, N.; Calderó, G.; García-Celma, M. J.; Solans, C.

2015-07-01

Polymeric nanoparticles could be promising drug delivery systems to treat neurodegenerative diseases. Among the various methods of nanoparticle preparation, nano-emulsion templating was used in the present study to prepare galantamine-loaded nano-emulsions by a low-energy emulsification method followed by solvent evaporation to obtain galantamine-loaded polymeric nanoparticles. This approach was found to be suitable because biocompatible, biodegradable and safe nanoparticles with appropriate features (hydrodynamic radii around 20 nm, negative surface charge and stability higher than 3 months) for their intravenous administration were obtained. Encapsulation efficiencies higher than 90 wt% were obtained with a sustained drug release profile as compared to that from aqueous and micellar solutions. The enzymatic activity of the drug was maintained at 80% after its encapsulation into nanoparticles that were non-cytotoxic at the required therapeutic concentration. Therefore, novel galantamine-loaded polymeric nanoparticles have been designed for the first time using the nano-emulsification approach and showed the appropriate features to become advanced drug delivery systems to treat neurodegenerative diseases.Polymeric nanoparticles could be promising drug delivery systems to treat neurodegenerative diseases. Among the various methods of nanoparticle preparation, nano-emulsion templating was used in the present study to prepare galantamine-loaded nano-emulsions by a low-energy emulsification method followed by solvent evaporation to obtain galantamine-loaded polymeric nanoparticles. This approach was found to be suitable because biocompatible, biodegradable and safe nanoparticles with appropriate features (hydrodynamic radii around 20 nm, negative surface charge and stability higher than 3 months) for their intravenous administration were obtained. Encapsulation efficiencies higher than 90 wt% were obtained with a sustained drug release profile as compared to that from aqueous and micellar solutions. The enzymatic activity of the drug was maintained at 80% after its encapsulation into nanoparticles that were non-cytotoxic at the required therapeutic concentration. Therefore, novel galantamine-loaded polymeric nanoparticles have been designed for the first time using the nano-emulsification approach and showed the appropriate features to become advanced drug delivery systems to treat neurodegenerative diseases. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03474d

Production efficiency of micellar casein concentrate using polymeric spiral-wound microfiltration membranes.

PubMed

Beckman, S L; Zulewska, J; Newbold, M; Barbano, D M

2010-10-01

Most current research has focused on using ceramic microfiltration (MF) membranes for micellar casein concentrate production, but little research has focused on the use of polymeric spiral-wound (SW) MF membranes. A method for the production of a serum protein (SP)-reduced micellar casein concentrate using SW MF was compared with a ceramic MF membrane. Pasteurized (79°C, 18s) skim milk (1,100 kg) was microfiltered at 50°C [about 3 × concentration] using a 0.3-μm polyvinylidene fluoride spiral-wound membrane, bleed-and-feed, 3-stage process, using 2 diafiltration stages, where the retentate was diluted 1:2 with reverse osmosis water. Skim milk, permeate, and retentate were analyzed for SP content, and the reduction of SP from skim milk was determined. Theoretically, 68% of the SP content of skim milk can be removed using a single-stage 3× MF. If 2 subsequent water diafiltration stages are used, an additional 22% and 7% of the SP can be removed, respectively, giving a total SP removal of 97%. Removal of SP greater than 95% has been achieved using a 0.1-μm pore size ceramic uniform transmembrane pressure (UTP) MF membrane after a 3-stage MF with diafiltration process. One stage of MF plus 2 stages of diafiltration of 50°C skim milk using a polyvinylidene fluoride polymeric SW 0.3-μm membrane yielded a total SP reduction of only 70.3% (stages 1, 2, and 3: 38.6, 20.8, and 10.9%, respectively). The SP removal rate for the polymeric SW MF membrane was lower in all 3 stages of processing (stages 1, 2, and 3: 0.05, 0.04, and 0.03 kg/m(2) per hour, respectively) than that of the comparable ceramic UTP MF membrane (stages 1, 2, and 3: 0.30, 0.11, and 0.06 kg/m(2) per hour, respectively), indicating that SW MF is less efficient at removing SP from 50°C skim milk than the ceramic UTP system. To estimate the number of steps required for the SW system to reach 95% SP removal, the third-stage SP removal rate (27.4% of the starting material SP content) was used to extrapolate that an additional 5 water diafiltration stages would be necessary, for a total of 8 stages, to remove 95% of the SP from skim milk. The 8-plus stages necessary to remove >95% SP for the SW MF membrane would create more permeate and a lengthier process than required with ceramic membranes. Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Stimulus sensitive gel with radioisotope and methods of making

DOEpatents

Weller, Richard E.; Lind, Michael A.; Fisher, Darrell R.; Gutowska, Anna; Campbell, Allison A.

2005-03-22

The present invention is a thermally reversible stimulus-sensitive gel or gelling copolymer radioisotope carrier that is a linear random copolymer of an [meth-]acrylamide derivative and a hydrophilic comonomer, wherein the linear random copolymer is in the form of a plurality of linear chains having a plurality of molecular weights greater than or equal to a minimum gelling molecular weight cutoff. Addition of a biodegradable backbone and/or a therapeutic agent imparts further utility. The method of the present invention for making a thermally reversible stimulus-sensitive gelling copolymer radionuclcide carrier has the steps of: (a) mixing a stimulus-sensitive reversible gelling copolymer with an aqueous solvent as a stimulus-sensitive reversible gelling solution; and (b) mixing a radioisotope with said stimulus-sensitive reversible gelling solution as said radioisotope carrier. The gel is enhanced by either combining it with a biodegradable backbone and/or a therapeutic agent in a gelling solution made by mixing the copolymer with an aqueous solvent.

Stimulus sensitive gel with radioisotope and methods of making

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weller, Richard E; Lind, Michael A; Fisher, Darrell R

2001-10-02

The present invention is a thermally reversible stimulus-sensitive gel or gelling copolymer radioisotope carrier that is a linear random copolymer of an [meth]acrylamide derivative and a hydrophilic comonomer, wherein the linear random copolymer is in the form of a plurality of linear chains having a plurality of molecular weights greater than or equal to a minimum gelling molecular weight cutoff. Addition of a biodegradable backbone and/or a therapeutic agent imparts further utility. The method of the present invention for making a thermally reversible stimulus-sensitive gelling copolymer radionuclcide carrier has the steps of: (a) mixing a stimulus-sensitive reversible gelling copolymer withmore » an aqueous solvent as a stimulus-sensitive reversible gelling solution; and (b) mixing a radioisotope with said stimulus-sensitive reversible gelling solution as said radioisotope carrier. The gel is enhanced by either combining it with a biodegradable backbone and/or a therapeutic agent in a gelling solution made by mixing the copolymer with an aqueous solvent.« less

Relaxation times and modes of disturbed aggregate distribution in micellar solutions with fusion and fission of micelles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zakharov, Anatoly I.; Adzhemyan, Loran Ts.; Shchekin, Alexander K., E-mail: akshch@list.ru

2015-09-28

We have performed direct numerical calculations of the kinetics of relaxation in the system of surfactant spherical micelles under joint action of the molecular mechanism with capture and emission of individual surfactant molecules by molecular aggregates and the mechanism of fusion and fission of the aggregates. As a basis, we have taken the difference equations of aggregation and fragmentation in the form of the generalized kinetic Smoluchowski equations for aggregate concentrations. The calculations have been made with using the droplet model of molecular surfactant aggregates and two modified Smoluchowski models for the coefficients of aggregate-monomer and aggregate-aggregate fusions which takemore » into account the effects of the aggregate size and presence of hydrophobic spots on the aggregate surface. A full set of relaxation times and corresponding relaxation modes for nonequilibrium aggregate distribution in the aggregation number has been found. The dependencies of these relaxation times and modes on the total concentration of surfactant in the solution and the special parameter controlling the probability of fusion in collisions of micelles with other micelles have been studied.« less

Cloud point phenomena for POE-type nonionic surfactants in a model room temperature ionic liquid.

PubMed

Inoue, Tohru; Misono, Takeshi

2008-10-15

The cloud point phenomenon has been investigated for the solutions of polyoxyethylene (POE)-type nonionic surfactants (C(12)E(5), C(12)E(6), C(12)E(7), C(10)E(6), and C(14)E(6)) in 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF(4)), a typical room temperature ionic liquid (RTIL). The cloud point, T(c), increases with the elongation of the POE chain, while decreases with the increase in the hydrocarbon chain length. This demonstrates that the solvophilicity/solvophobicity of the surfactants in RTIL comes from POE chain/hydrocarbon chain. When compared with an aqueous system, the chain length dependence of T(c) is larger for the RTIL system regarding both POE and hydrocarbon chains; in particular, hydrocarbon chain length affects T(c) much more strongly in the RTIL system than in equivalent aqueous systems. In a similar fashion to the much-studied aqueous systems, the micellar growth is also observed in this RTIL solvent as the temperature approaches T(c). The cloud point curves have been analyzed using a Flory-Huggins-type model based on phase separation in polymer solutions.

Solution Structure and Membrane Interaction of the Cytoplasmic Tail of HIV-1 gp41 Protein.

PubMed

Murphy, R Elliot; Samal, Alexandra B; Vlach, Jiri; Saad, Jamil S

2017-11-07

The cytoplasmic tail of gp41 (gp41CT) remains the last HIV-1 domain with an unknown structure. It plays important roles in HIV-1 replication such as mediating envelope (Env) intracellular trafficking and incorporation into assembling virions, mechanisms of which are poorly understood. Here, we present the solution structure of gp41CT in a micellar environment and characterize its interaction with the membrane. We show that the N-terminal 45 residues are unstructured and not associated with the membrane. However, the C-terminal 105 residues form three membrane-bound amphipathic α helices with distinctive structural features such as variable degree of membrane penetration, hydrophobic and basic surfaces, clusters of aromatic residues, and a network of cation-π interactions. This work fills a major gap by providing the structure of the last segment of HIV-1 Env, which will provide insights into the mechanisms of Gag-mediated Env incorporation as well as the overall Env mobility and conformation on the virion surface. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spatially-resolved magnetic resonance study of the dissolution interface between soaps and water

NASA Astrophysics Data System (ADS)

Ciampi, E.; Goerke, U.; McDonald, P. J.; Chambers, J. G.; Newling, B.

2002-06-01

The developing interfacial region between a soap bar and water has been studied using a suite of spatially resolved NMR techniques. Stray field imaging (STRAFI) allowed the dynamics of water ingress into a shop-bought, commercial soap to be followed. A simplistic analysis of the data shows the ingress to be a Fickian process (∝t1/2) in the first 4 h. The T2 contrast employed in the STRAFI method is not sufficient to resolve detail of the mesophase formation at the interface. However, double quantum filtered 2H spectroscopy at different positions in the interfacial region allowed water concentration (and mesophase distribution) to be mapped over the first 120 h of dissolution. A simple model shows good agreement with the water concentration data. In the isotropic soap solution above the interfacial region, J-cyclic cross polarization was used to selectively interrogate the CH2 1H of the soap alkyl chains and, in combination with a pulsed field gradient measurement of self-diffusion, suggests a micellar solution in which the hydrodynamic radius of the micelles is ~5nm.

Self-assembly behaviour of colistin and its prodrug colistin methanesulfonate: implications for solution stability and solubilization

PubMed Central

Wallace, Stephanie J.; Li, Jian; Nation, Roger L.; Prankerd, Richard J.; Velkov, Tony; Boyd, Ben J.

2010-01-01

Colistin is an amphiphilic antibiotic that has re-emerged into clinical use due to the increasing prevalence of difficult-to-treat Gram-negative infections. The existence of self-assembling colloids in solutions of colistin and its derivative prodrug, colistin methanesulfonate (CMS) was investigated. Colistin and CMS reduced the air-water interfacial tension, and dynamic light scattering (DLS) studies showed the existence of 2.07 ± 0.3 nm aggregates above 1.5 mM for colistin, and of 1.98 ± 0.36 nm aggregates for CMS above 3.5 mM (mean ± SD). Above the respective critical micelle concentrations (CMC) the solubility of azithromycin, a hydrophobic antibiotic, increased approximately linearly with increasing surfactant concentration (5:1 mol ratio colistin:azithromycin), suggestive of hydrophobic domains within the micellar cores. Rapid conversion of CMS to colistin occurred below the CMC (60 % over 48 hr), while conversion above the CMC was less than 1 %. The formation of colistin and CMS micelles demonstrated in this study is the proposed mechanism for solubilization of azithromycin and the concentration-dependent stability of CMS. PMID:20302384

A comparison between the electrochemical behavior of reversible magnesium and lithium electrodes

NASA Astrophysics Data System (ADS)

Aurbach, D.; Gofer, Y.; Schechter, A.; Chusid, O.; Gizbar, H.; Cohen, Y.; Moshkovich, M.; Turgeman, R.

This paper describes briefly the difference between reversible lithium and magnesium electrodes. In the case of lithium, the active metal is always covered by surface films. Li dissolution-deposition is reversible only when the surface films contain elastomers and are flexible. Hence, they can accommodate the morphological changes of the electrode during the electrochemical processes without breaking down. In an ideal situation, lithium is deposited beneath the surface films, while being constantly protected in a way that prevents reactions between freshly deposited lithium and solution species. In contrast to lithium, magnesium electrodes are reversible only in solutions where surface film free conditions exist. Mg does not react with ethers, and thus, in ethereal solutions of Grignard reagents (RMgX, where R=alkyl, aryl, X=halide) and complexes of the following type: Mg(AlX 4- nR n' R n″ ') 2, R and R'=alkyl groups, X=halide, A=Al, 0< n<4 and n'+ n''= n, magnesium electrodes behave reversibly. However, it should be noted that the above stoichiometry of the Mg salts does not reflect the true structure of the active ions in solutions. Mg deposition does not occur via electron transfer to simply solvated Mg 2+ ions. The behavior of Mg electrodes in these solutions is discussed in light of studies by EQCM, EIS, FTIR, XPS, STM and standard electrochemical techniques.

Reversible Hydrogel–Solution System of Silk with High Beta-Sheet Content

PubMed Central

2015-01-01

Silkworm silk has been widely used as a textile fiber, as biomaterials and in optically functional materials due to its extraordinary properties. The β-sheet-rich natural nanofiber units of about 10–50 nm in diameter are often considered the origin of these properties, yet it remains unclear how silk self-assembles into these hierarchical structures. A new system composed of β-sheet-rich silk nanofibers about 10–20 nm in diameter is reported here, where these nanofibers formed into “flowing hydrogels” at 0.5–2% solutions and could be transformed back into the solution state at lower concentrations, even with a high β-sheet content. This is in contrast with other silk processed materials, where significant β-sheet content negates reversibility between solution and solid states. These fibers are formed by regulating the self-assembly process of silk in aqueous solution, which changes the distribution of negative charges while still supporting β-sheet formation in the structures. Mechanistically, there appears to be a shift toward negative charges along the outside of the silk nanofibers in our present study, resulting in a higher zeta potential (above −50 mV) than previous silk materials which tend to be below −30 mV. The higher negative charge on silk nanofibers resulted in electrostatic repulsion strong enough to negate further assembly of the nanofibers. Changing silk concentration changed the balance between hydrophobic interactions and electrostatic repulsion of β-sheet-rich silk nanofibers, resulting in reversible hydrogel–solution transitions. Furthermore, the silk nanofibers could be disassembled into shorter fibers and even nanoparticles upon ultrasonic treatment following the transition from hydrogel to solution due to the increased dispersion of hydrophobic smaller particles, without the loss of β-sheet content, and with retention of the ability to transition between hydrogel and solution states through reversion to longer nanofibers during self-assembly. These reversible solution-hydrogel transitions were tunable with ultrasonic intensity, time, or temperature. PMID:25056606

Reversible hydrogel-solution system of silk with high beta-sheet content.

PubMed

Bai, Shumeng; Zhang, Xiuli; Lu, Qiang; Sheng, Weiqin; Liu, Lijie; Dong, Boju; Kaplan, David L; Zhu, Hesun

2014-08-11

Silkworm silk has been widely used as a textile fiber, as biomaterials and in optically functional materials due to its extraordinary properties. The β-sheet-rich natural nanofiber units of about 10-50 nm in diameter are often considered the origin of these properties, yet it remains unclear how silk self-assembles into these hierarchical structures. A new system composed of β-sheet-rich silk nanofibers about 10-20 nm in diameter is reported here, where these nanofibers formed into "flowing hydrogels" at 0.5-2% solutions and could be transformed back into the solution state at lower concentrations, even with a high β-sheet content. This is in contrast with other silk processed materials, where significant β-sheet content negates reversibility between solution and solid states. These fibers are formed by regulating the self-assembly process of silk in aqueous solution, which changes the distribution of negative charges while still supporting β-sheet formation in the structures. Mechanistically, there appears to be a shift toward negative charges along the outside of the silk nanofibers in our present study, resulting in a higher zeta potential (above -50 mV) than previous silk materials which tend to be below -30 mV. The higher negative charge on silk nanofibers resulted in electrostatic repulsion strong enough to negate further assembly of the nanofibers. Changing silk concentration changed the balance between hydrophobic interactions and electrostatic repulsion of β-sheet-rich silk nanofibers, resulting in reversible hydrogel-solution transitions. Furthermore, the silk nanofibers could be disassembled into shorter fibers and even nanoparticles upon ultrasonic treatment following the transition from hydrogel to solution due to the increased dispersion of hydrophobic smaller particles, without the loss of β-sheet content, and with retention of the ability to transition between hydrogel and solution states through reversion to longer nanofibers during self-assembly. These reversible solution-hydrogel transitions were tunable with ultrasonic intensity, time, or temperature.

NUMERICAL TECHNIQUES TO SOLVE CONDENSATIONAL AND DISSOLUTIONAL GROWTH EQUATIONS WHEN GROWTH IS COUPLED TO REVERSIBLE REACTIONS (R823186)

EPA Science Inventory

Noniterative, unconditionally stable numerical techniques for solving condensational and
dissolutional growth equations are given. Growth solutions are compared to Gear-code solutions for
three cases when growth is coupled to reversible equilibrium chemistry. In all cases, ...

An approximate stationary solution for multi-allele neutral diffusion with low mutation rates.

PubMed

Burden, Conrad J; Tang, Yurong

2016-12-01

We address the problem of determining the stationary distribution of the multi-allelic, neutral-evolution Wright-Fisher model in the diffusion limit. A full solution to this problem for an arbitrary K×K mutation rate matrix involves solving for the stationary solution of a forward Kolmogorov equation over a (K-1)-dimensional simplex, and remains intractable. In most practical situations mutations rates are slow on the scale of the diffusion limit and the solution is heavily concentrated on the corners and edges of the simplex. In this paper we present a practical approximate solution for slow mutation rates in the form of a set of line densities along the edges of the simplex. The method of solution relies on parameterising the general non-reversible rate matrix as the sum of a reversible part and a set of (K-1)(K-2)/2 independent terms corresponding to fluxes of probability along closed paths around faces of the simplex. The solution is potentially a first step in estimating non-reversible evolutionary rate matrices from observed allele frequency spectra. Copyright © 2016 Elsevier Inc. All rights reserved.

Microemulsions and Aggregation Formation in Extraction Processes for Used Nuclear Fuel: Thermodynamic and Structural Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nilsson, Mikael

Advanced nuclear fuel cycles rely on successful chemical separation of various elements in the used fuel. Numerous solvent extraction (SX) processes have been developed for the recovery and purification of metal ions from this used material. However, the predictability of process operations has been challenged by the lack of a fundamental understanding of the chemical interactions in several of these separation systems. For example, gaps in the thermodynamic description of the mechanism and the complexes formed will make predictions very challenging. Recent studies of certain extraction systems under development and a number of more established SX processes have suggested thatmore » aggregate formation in the organic phase results in a transformation of its selectivity and efficiency. Aggregation phenomena have consistently been interfering in SX process development, and have, over the years, become synonymous with an undesirable effect that must be prevented. This multiyear, multicollaborative research effort was carried out to study solvation and self-organization in non-aqueous solutions at conditions promoting aggregation phenomena. Our approach to this challenging topic was to investigate extraction systems comprising more than one extraction reagent where synergy of the metal ion could be observed. These systems were probed for the existence of stable microemulsions in the organic phase, and a number of high-end characterization tools were employed to elucidate the role of the aggregates in metal ion extraction. The ultimate goal was to find connections between synergy of metal ion extraction and reverse micellar formation. Our main accomplishment for this project was the expansion of the understanding of metal ion complexation in the extraction system combining tributyl phosphate (TBP) and dibutyl phosphoric acid (HDBP). We have found that for this system no direct correlation exists for the metal ion extraction and the formation of aggregates, meaning that the metal ion is not solubilized in a reverse micelle core. Rather we have found solid evidence that the metal ions are extracted and coordinated by the organic ligands as suggested by classic SX theories. However, we have challenged the existence of mixed complexes that have been suggested to exist in this particular extraction system. Most importantly we have generated a wealth of information and trained students on important lab techniques and strengthened the collaboration between the DOE national laboratories and US educational institution involved in this work.« less

Inverse hexagonal and cubic micellar lyotropic liquid crystalline phase behaviour of novel double chain sugar-based amphiphiles.

PubMed

Feast, George C; Lepitre, Thomas; Tran, Nhiem; Conn, Charlotte E; Hutt, Oliver E; Mulet, Xavier; Drummond, Calum J; Savage, G Paul

2017-03-01

The lyotropic phase behaviour of a library of sugar-based amphiphiles was investigated using high-throughput small-angle X-ray scattering (SAXS). Double unsaturated-chain monosaccharide amphiphiles formed inverse hexagonal and cubic micellar (Fd3m) lyotropic phases under excess water conditions. A galactose-oleyl amphiphile from the library was subsequently formulated into hexosome nanoparticles, which have potential uses as drug delivery vehicles. The nanoparticles were shown to be stable at elevated temperatures and non-cytotoxic up to at least 200μgmL -1 . Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Simultaneous analysis of tea catechins, caffeine, gallic acid, theanine and ascorbic acid by micellar electrokinetic capillary chromatography.

PubMed

Aucamp, J P; Hara, Y; Apostolides, Z

2000-04-21

A micellar electrokinetic capillary chromatography (MEKC) method for the simultaneous analysis of five tea catechins, theanine, caffeine, gallic acid and ascorbic acid has been developed. The catechins are (-)-epicatechin, (+)-catechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate. p-Nitrophenol serves as both reference and internal standard. All the components are separated within 13 min with a 57 cm uncoated fused-silica column. On-column detection was carried out at 200 nm. This method has been used to measure these compounds in fresh tea leaves and tea liquor. The limit of detection for all analytes ranged from 1 to 20 microg/ml.

Membrane solubilisation and reconstitution by octylglucoside: comparison of synthetic lipid and natural lipid extract by isothermal titration calorimetry.

PubMed

Krylova, Oxana O; Jahnke, Nadin; Keller, Sandro

2010-08-01

We have studied the solubilisation and reconstitution of lipid membranes composed of either synthetic phosphatidylcholine or Escherichia. coli polar lipid extract by the non-ionic detergent octylglucoside. For both lipid systems, composition-dependent transformations of unilamellar vesicles into micelles or vice versa were followed by high-sensitivity isothermal titration calorimetry. Data obtained over a range of detergent and lipid concentrations could be rationalised in terms of a three-stage phase separation model involving bilayer, bilayer/micelle coexistence, and micellar ranges, yielding the detergent/lipid phase diagrams and the bilayer-to-micelle partition coefficients of both detergent and lipid. The most notable difference between the lipids investigated was a substantial widening of the bilayer/micelle coexistence range for E. coli lipid, which was due to an increased preference of the detergent and a decreased affinity of the lipid for the micellar phase as compared with the bilayer phase. These effects on the bilayer-to-micelle partition coefficients could be explained by the high proportion in E. coli membranes of lipids possessing negative spontaneous curvature, which hampers both their transfer into strongly curved micellar structures as well as the insertion of detergent into condensed bilayers.

Statistical thermodynamics of amphiphile chains in micelles

PubMed Central

Ben-Shaul, A.; Szleifer, I.; Gelbart, W. M.

1984-01-01

The probability distribution of amphiphile chain conformations in micelles of different geometries is derived through maximization of their packing entropy. A lattice model, first suggested by Dill and Flory, is used to represent the possible chain conformations in the micellar core. The polar heads of the chains are assumed to be anchored to the micellar surface, with the other chain segments occupying all lattice sites in the interior of the micelle. This “volume-filling” requirement, the connectivity of the chains, and the geometry of the micelle define constraints on the possible probability distributions of chain conformations. The actual distribution is derived by maximizing the chain's entropy subject to these constraints; “reversals” of the chains back towards the micellar surface are explicitly included. Results are presented for amphiphiles organized in planar bilayers and in cylindrical and spherical micelles of different sizes. It is found that, for all three geometries, the bond order parameters decrease as a function of the bond distance from the polar head, in accordance with recent experimental data. The entropy differences associated with geometrical changes are shown to be significant, suggesting thereby the need to include curvature (environmental)-dependent “tail” contributions in statistical thermodynamic treatments of micellization. PMID:16593492

Slow molecular dynamics of water in a lyotropic complex fluid studied by deuterium conventional and spin-lattice relaxometry NMR.

PubMed

Rodríguez, C R; Pusiol, D J; Figueiredo Neto, A M; Seitter, R-O

2002-03-01

A nuclear magnetic resonance study of protons and deuterons in the mesomorphic phases of the micellar lyotropic mixture potassium laurate/1-decanol/heavy water is reported. The slow dynamical behavior of water molecules has been investigated with deuterons spin-lattice relaxation dispersion in the Larmor frequency range 10(3)

Determination of adulteration of malachite green in green pea and some prepared foodstuffs by micellar liquid chromatography.

PubMed

Ashok, Vipin; Agrawal, Nitasha; Durgbanshi, Abhilasha; Esteve-Romero, Josep; Bose, Devasish

2014-01-01

A simple, fast, and robust micellar LC method was developed for the separation and identification of the nonpermitted color malachite green in green pea and some ready-to-eat foodstuffs. Malachite green (4-[(4-dimethylaminophenyl) phenyl-methyl]-N,N-dimethylaniline) is a hazardous dye that is used to treat fungal and protozoan infections in fish and is a common adulterant (coloring agent) in green pea and other green vegetables because of its green color. In the present work, malachite green was determined in various foodstuffs using a direct injection technique on an RP C18 column with isocratic elution. The optimum mobile phase consisted of 0.15 M sodium dodecyl sulfate (SDS), 6% pentanol buffered at pH 5. Detection was carried out at 620 nm. Malachite green was eluted in 9.2 min without any interference caused by endogenous compounds. Linearities (r > 0.9999), intraday and interday precision (RSD less than 1.00%) in micellar media, and robustness were studied for method validation. LOD and LOQ were 0.10 and 0.25 ppm, respectively. The simplicity of the developed method makes it useful for routine analysis in the area of food QC.

Impact of Surface Active Ionic Liquids on the Cloud Points of Nonionic Surfactants and the Formation of Aqueous Micellar Two-Phase Systems.

PubMed

Vicente, Filipa A; Cardoso, Inês S; Sintra, Tânia E; Lemus, Jesus; Marques, Eduardo F; Ventura, Sónia P M; Coutinho, João A P

2017-09-21

Aqueous micellar two-phase systems (AMTPS) hold a large potential for cloud point extraction of biomolecules but are yet poorly studied and characterized, with few phase diagrams reported for these systems, hence limiting their use in extraction processes. This work reports a systematic investigation of the effect of different surface-active ionic liquids (SAILs)-covering a wide range of molecular properties-upon the clouding behavior of three nonionic Tergitol surfactants. Two different effects of the SAILs on the cloud points and mixed micelle size have been observed: ILs with a more hydrophilic character and lower critical packing parameter (CPP < 1 / 2 ) lead to the formation of smaller micelles and concomitantly increase the cloud points; in contrast, ILs with a more hydrophobic character and higher CPP (CPP ≥ 1) induce significant micellar growth and a decrease in the cloud points. The latter effect is particularly interesting and unusual for it was accepted that cloud point reduction is only induced by inorganic salts. The effects of nonionic surfactant concentration, SAIL concentration, pH, and micelle ζ potential are also studied and rationalized.

Effects of curcumin in pediatric epithelial liver tumors: inhibition of tumor growth and alpha-fetoprotein in vitro and in vivo involving the NFkappaB- and the beta-catenin pathways

PubMed Central

Bortel, Nicola; Armeanu-Ebinger, Sorin; Schmid, Evi; Kirchner, Bettina; Frank, Jan; Kocher, Alexa; Schiborr, Christina; Warmann, Steven; Fuchs, Jörg; Ellerkamp, Verena

2015-01-01

In children with hepatocellular carcinoma (pHCC) the 5-year overall survival rate is poor. Effects of cytostatic therapies such as cisplatin and doxorubicin are limited due to chemoresistance and tumor relapse. In adult HCC, several antitumor properties are described for the use of curcumin. Curcumin is one of the best-investigated phytochemicals in complementary oncology without relevant side effects. Its use is limited by low bioavailability. Little is known about the influence of curcumin on pediatric epithelial hepatic malignancies. We investigated the effects of curcumin in combination with cisplatin on two pediatric epithelial liver tumor cell lines. As mechanisms of action inhibition of NFkappaB, beta-catenin, and decrease of cyclin D were identified. Using a mouse xenograft model we could show a significant decrease of alpha-fetoprotein after combination therapy of oral micellar curcumin and cisplatin. Significant concentrations of curcuminoids were found in blood samples, organ lysates, and tumor tissue after oral micellar curcumin administration. Micellar curcumin in combination with cisplatin can be a promising strategy for treatment of pediatric HCC. PMID:26515460

Synthesis, characterisation and physicochemical properties of hydrophobically modified inulin using long-chain fatty acyl chlorides.

PubMed

Han, Lingyu; Ratcliffe, I; Williams, P A

2017-12-15

A series of inulin derivatives were synthesized in aqueous solution using acyl chlorides with varying alkyl chain length (C10-C16). They were characterised using a number of techniques including MALDI TOF-MS, 1 H NMR and FTIR and their degree of substitution determined. The solution properties of the hydrophobically modified inulins were investigated using dye solubilisation and surface tension and it was confirmed that the molecules aggregated in solution above a critical concentration (critical aggregation concentration, CAC). The value of the CAC was found to be reasonably consistent between the different techniques and was shown to decrease with increasing hydrophobe chain length. It was found that the C10, C12 and C14 derivatives formed stable oil-in-water emulsions and the emulsion droplet size decreased with increasing alkyl chain length. The C16 derivative was not able to produce stable oil-in-water emulsions; however, it was able to form stable water-in-oil emulsions. The fact that the derivatives are able to form micellar-like aggregates and stabilise emulsions makes them suitable candidates for the encapsulation and delivery of active compounds with potential application in food, cosmetic, personal care and pharmaceutical formulations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Diffusing wave spectroscopy in Maxwellian fluids.

PubMed

Galvan-Miyoshi, J; Delgado, J; Castillo, R

2008-08-01

We present a critical assessment of the diffusing wave spectroscopy (DWS) technique for obtaining the characteristic lengths and for measuring the loss and storage moduli of a reasonable well-known wormlike micelle (WM) system. For this purpose, we tracked the Brownian motion of particles using DWS embedded in a Maxwellian fluid constituted by a wormlike micellar solution made of cetyltrimethylammonium bromide (CTAB), sodium salicylate (NaSal), and water. We found that the motion of particles was governed by the viscosity of the solvent at short times and by the stress relaxation mechanisms of the giant micelles at longer times. From the time evolution of the mean square displacement of particles, we could obtain for the WM solution the cage size where each particle is harmonically bound at short times, the long-time diffusion coefficient, and experimental values for the exponent that accounts for the broad spectrum of relaxation times at the plateau onset time found in the (deltar2(t)) vs. time curves. In addition, from the (deltar2(t)) vs. time curves, we obtained G'(omega) and G"(omega) for the WM solutions. All the DWS microreological information allowed us to estimate the characteristic lengths of the WM network. We compare our DWS microrheological results and characteristic lengths with those obtained with mechanical rheometers at different NaSal/CTAB concentration ratios and temperatures.

Antioxidant and antimicrobial activities of clove bud essential oil and eugenol nanoparticles in alcohol-free microemulsion.

PubMed

Hamed, Said Fatouh; Sadek, Zainab; Edris, Amr

2012-01-01

Clove bud essential oil (CEO) and its major individual phenolic constituent eugenol were formulated as nanoparticles in water-based microemulsion systems. The oil titration method was used to incorporate different amounts of the oil and eugenol in the micellar solution of Tween-20. The Antioxidant and antimicrobial activities were evaluated using the DPPH* free radical scavenging assay and the agar disc dilution method, respectively. Results showed that microemulsion improved the evaluated activities of CEO and eugenol compared with the crude counterparts. Individual eugenol microemulsion was more effective than CEO microemulsion which contained only 61.7% eugenol among its constituents. The results of this study could have potential applications in water-based disinfectants, preservation and flavoring of food and in personal hygiene products. It may also have promising applications in the nutraceutical and functional beverage field.

Electrochemical Detection of Nicotine Using Cerium Nanoparticles Modified Carbon Paste Sensor and Anionic Surfactant

NASA Astrophysics Data System (ADS)

Fekry, A. M.; Azab, S. M.; Shehata, M.; Ameer, M. A.

A promising electrochemical sensor for the determination of nicotine (NIC) was developed by electrodeposition of Ce-Nanoparticles on a carbon paste electrode (CPE). The interaction of nicotine was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Scanning electron microscope (SEM) and Energy Dispersive X-Ray Analysis (EDX) techniques, in both aqueous and micellar media. The NIC Measurements were carried out in Britton-Robinson (B-R) buffer solution of pH range (2.0-8.0) containing (1.0 mM) sodium dodecylsulfate (SDS). The linear response range of the sensor was between 8 × 10-6 and 10-4 M with a detection limit of 9.43 × 10-8 M. Satisfactory results were achieved for the detection of NIC in real samples as urine and different brands of commercial cigarettes.

Non-ionic block copolymers leading to a highly ordered organosilica material

NASA Astrophysics Data System (ADS)

Rebbin, V.; Rothkirch, A.; Vainio, U.; Funari, S. S.

2012-03-01

Phenylene-bridged periodic mesoporous organosilica (PMO) materials with hexaethylene glycol mono hexadecylether (C16(EO)6) as structure directing agent (SDA) in acidic solution were synthesised and the reaction was studied in different conditions, including in situ small angle X-ray scattering at room temperature and at 60 °C. The in situ SAXS investigations at 60 °C show the formation of a 2D hexagonal mesostructure after 3 hours reaction time. In contrast to these results the same reaction performed in the laboratory produced a powder that, after drying at room temperature, shows a large number of diffraction peaks, allowing identifying a lamellar structure, possibly in coexistence of a micellar cubic structure (space group Pm3n). Aposteriori removal of the surfactant from the powder synthesised in the laboratory led to the collapse of the lamellar structure.

Modification of Encapsulation Pressure of Reverse Micelles in Liquid Ethane

PubMed Central

Peterson, Ronald W.; Nucci, Nathaniel V.; Wand, A. Joshua

2011-01-01

Encapsulation of within reverse micelles dissolved in low viscosity fluids offers a potential solution to the slow tumbling problem presented by large soluble macromolecules to solution NMR spectroscopy. The reduction in effective macromolecular tumbling is directly dependent upon the viscosity of the solvent. Liquid ethane is of sufficiently low viscosity at pressures below 5,000 p.s.i. to offer a significant advantage. Unfortunately, the viscosity of liquid ethane shows appreciable pressure dependence. Reverse micelle encapsulation in liquid ethane often requires significantly higher pressures, which obviates the potential advantages offered by liquid ethane over liquid propane. Addition of co-surfactants or co-solvents can be used to manipulate the minimum pressure required to obtain stable, well-behaved solutions of reverse micelles prepared in liquid ethane. A library of potential additives is examined and several candidates suitable for use with encapsulated proteins are described. PMID:21764613

Modification of encapsulation pressure of reverse micelles in liquid ethane.

PubMed

Peterson, Ronald W; Nucci, Nathaniel V; Wand, A Joshua

2011-09-01

Encapsulation within reverse micelles dissolved in low viscosity fluids offers a potential solution to the slow tumbling problem presented by large soluble macromolecules to solution NMR spectroscopy. The reduction in effective macromolecular tumbling is directly dependent upon the viscosity of the solvent. Liquid ethane is of sufficiently low viscosity at pressures below 5000 psi to offer a significant advantage. Unfortunately, the viscosity of liquid ethane shows appreciable pressure dependence. Reverse micelle encapsulation in liquid ethane often requires significantly higher pressures, which obviates the potential advantages offered by liquid ethane over liquid propane. Addition of co-surfactants or co-solvents can be used to manipulate the minimum pressure required to obtain stable, well-behaved solutions of reverse micelles prepared in liquid ethane. A library of potential additives is examined and several candidates suitable for use with encapsulated proteins are described. Copyright © 2011 Elsevier Inc. All rights reserved.

An eco-friendly stability-indicating spectrofluorimetric method for the determination of two anticancer stereoisomer drugs in their pharmaceutical preparations following micellar enhancement: Application to kinetic degradation studies.

PubMed

El-Kimary, Eman I; El-Yazbi, Amira F

2016-06-15

A new rapid and highly sensitive stability-indicating spectrofluorimetric method was developed for the determination of two stereoisomers anticancer drugs, doxorubicin (DOX) and epirubicin (EPI) in pure form and in pharmaceutical preparations. The fluorescence spectral behavior of DOX and EPI in a sodium dodecyl sulfate (SDS) micellar system was investigated. It was found that the fluorescence intensity of DOX and EPI in an aqueous solution of phosphate buffer pH4.0 and in the presence of SDS was greatly (about two fold) enhanced and the mechanism of fluorescence enhancement effect of SDS on DOX was also investigated. The fluorescence intensity of DOX or EPI was measured at 553nm after excitation at 497nm. The plots of fluorescence intensity versus concentration were rectilinear over a range of 0.03-2μg/mL for both DOX and EPI with good correlation coefficient (r>0.999). High sensitivity to DOX and EPI was attained using the proposed method with limits of detection of 10 and 9ng/mL and limits of quantitation of 29 and 28ng/mL, for DOX and EPI, respectively. The method was successfully applied for the determination of DOX and EPI in biological fluids and in their commercial pharmaceutical preparations and the results were concordant with those obtained using a previously reported method. The application of the proposed method was extended to stability studies of DOX following different forced degradation conditions (acidic, alkaline, oxidative and photolytic) according to ICH guidelines. Moreover, the kinetics of the alkaline and oxidative degradation of DOX was investigated and the apparent first-order rate constants and half-life times were calculated. Copyright © 2016 Elsevier B.V. All rights reserved.

Design of pH-sensitive methotrexate prodrug-targeted curcumin nanoparticles for efficient dual-drug delivery and combination cancer therapy.

PubMed

Xie, Jiajiang; Fan, Zhongxiong; Li, Yang; Zhang, Yinying; Yu, Fei; Su, Guanghao; Xie, Liya; Hou, Zhenqing

2018-01-01

We designed acid-labile methotrexate (MTX) targeting prodrug self-assembling nanoparticles loaded with curcumin (CUR) drug for simultaneous delivery of multi-chemotherapeutic drugs and combination cancer therapy. A dual-acting MTX, acting as both an anticancer drug and as a tumor-targeting ligand, was coupled to 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[aldehyde(polyethylene glycol)-2000] via Schiff's base reaction. The synthesized prodrug conjugate (DSPE-PEG-Imine-MTX) could be self-assembled into micellar nanoparticles (MTX-Imine-M) in aqueous solution, which encapsulated CUR into their core by hydrophobic interactions (MTX-Imine-M-CUR). The prepared MTX-Imine-M-CUR nanoparticles were composed of an inner hydrophobic DSPE/CUR core and an outside hydrophilic bishydroxyl poly (ethyleneglycol) (PEG) shell with a self-targeting MTX prodrug corona. The imine linker between 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[aldehyde(polyethyleneglycol)-2000] and MTX, as a dynamic covalent bond, was strong enough to remain intact in physiological pH, even though it is rapidly cleaved in acidic pH. The MTX-Imine-M-CUR could codeliver MTX and CUR selectively and efficiently into the cancer cells via folate receptor-mediated endocytosis followed by the rapid intracellular release of CUR and the active form of MTX via the acidity of endosomes/lysosomes. Moreover, the MTX-Imine-M-CUR resulted in significantly higher in vitro and in vivo anticancer activity than pH-insensitive DSPE-PEGAmide-MTX assembling nanoparticles loaded with CUR (MTX-Amide-M-CUR), MTX unconjugated DSPE-PEG assembling micellar nanoparticles loaded with CUR (M-CUR), combination of both free drugs, and individual free drugs. The smart system provided a simple, yet feasible, drug delivery strategy for targeted combination chemotherapy.

Sphere-to-rod transition of non-surface-active amphiphilic diblock copolymer micelles: a small-angle neutron scattering study.

PubMed

Kaewsaiha, Ploysai; Matsumoto, Kozo; Matsuoka, Hideki

2007-08-28

Micellization behavior of amphiphilic diblock copolymers with strong acid groups, poly(hydrogenated isoprene)-block-poly(styrenesulfonate), was investigated by small-angle neutron scattering (SANS). We have reported previously (Kaewsaiha, P.; Matsumoto, K.; Matsuoka, H. Langmuir 2005, 21, 9938) that this strongly ionic amphiphilic diblock copolymer shows almost no surface activity but forms micelles in water. In this study, the size, shape, and internal structures of the micelles formed by these unique copolymers in aqueous solution were duly investigated. The SANS data were well described by the theoretical form factor of a core-shell model and the Pedersen core-corona model. The micellar shape strongly depends on the hydrophobic chain length of the block copolymer. The polymer with the shortest hydrophobic chain was suggested to form spherical micelles, whereas the scattering curves of the longer hydrophobic chain polymers showed a q-1 dependence, reflecting the formation of rodlike micelles. Furthermore, the addition of salt at high concentration also induced the sphere-to-rod transition in micellar shape as a result of the shielding effect of electrostatic repulsion. The corona thickness was almost constant up to the critical salt concentration (around 0.2 M) and then decreased with further increases in salt concentration, which is in qualitatively agreement with existing theories. The spherical/rodlike micelle ratio was also constant up to the critical salt concentration and then decreased. The micelle size and shape of this unique polymer could be described by the common concept of the packing parameter, but the anomalously stable nature of the micelle (up to 1 M NaCl) is a special characteristic.

Structural insights of a self-assembling 9-residue peptide from the C-terminal tail of the SARS corona virus E-protein in DPC and SDS micelles: A combined high and low resolution spectroscopic study.

PubMed

Ghosh, Anirban; Bhattacharyya, Dipita; Bhunia, Anirban

2018-02-01

In recent years, several studies based on the interaction of self-assembling short peptides derived from viroporins with model membranes, have improved our understanding of the molecular mechanism of corona virus (CoV) infection under physiological conditions. In this study, we have characterized the mechanism of membrane interaction of a short, 9-residue peptide TK9 (T 55 VYVYSRVK 63 ) that had been derived from the carboxyl terminal of the Severe Acute Respiratory Syndrome (SARS) corona virus (SARS CoV) envelope (E) protein. The peptide has been studied for its physical changes in the presence of both zwitterionic DPC and negatively charged SDS model membrane micelles, respectively, with the help of a battery of biophysical techniques including two-dimensional solution state NMR spectroscopy. Interestingly, in both micellar environments, TK9 adopted an alpha helical conformation; however, the helical propensities were much higher in the case of DPC compared to those of SDS micelle, suggesting that TK9 has more specificity towards eukaryotic cell membrane than the bacterial cell membrane. The orientation of the peptide TK9 also varies in the different micellar environments. The peptide's affinity was further manifested by its pronounced membrane disruption ability towards the mammalian compared to the bacterial membrane mimic. Collectively, the in-depth structural information on the interaction of TK9 with different membrane environments explains the host specificity and membrane orientation owing to subsequent membrane disruption implicated in the viral pathogenesis. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanosized complexation assemblies housed inside reverse micelles churn out monocytic delivery cores for bendamustine hydrochloride.

PubMed

Singh, Yuvraj; Chandrashekhar, Anumandla; Meher, Jaya Gopal; Durga Rao Viswanadham, K K; Pawar, Vivek K; Raval, Kavit; Sharma, Komal; Singh, Pankaj K; Kumar, Animesh; Chourasia, Manish K

2017-04-01

We explore a plausible method of targeting bendamustine hydrochloride (BM) to circulatory monocytes by exploiting their intrinsic endocytic/phagocytic capability. We do so by complexation of sodium alginate and chitosan inside dioctyl sulfo succinate sodium (AOT) reverse micelles to form bendamustine hydrochloride loaded nanoparticles (CANPs). Dynamic light scattering, electrophoretic mobility and UV spectroscopy were used to detail intra-micellar complexation dynamics and to prove that drug was co-captured during interaction of carbohydrate polymers. A fluorescent conjugate of drug (RBM) was used to trace its intracellular fate after its loading into nanoparticles. CANPs were sized below 150nm, had 75% drug entrapment and negative zeta potential (-30mV). Confocal microscopy demonstrated that developed chitosan alginate nanoparticles had the unique capability to carry BM specifically to its site of action. Quantitative and mechanism based cell uptake studies revealed that monocytes had voracious capacity to internalize CANPs via simultaneous scavenger receptor based endocytic and phagocytic mechanism. Comparative in vitro pharmacokinetic studies revealed obtainment of significantly greater intracellular drug levels when cells were treated with CANPs. This caused reduction in IC 50 (22.5±2.1μg/mL), enhancement in G 2 M cell cycle arrest, greater intracellular reactive oxygen species generation, and increased apopotic potential of bendamustine hydrochloride in THP-1 cells. Selective monocytic targeting of bendamustine hydrochloride using carbohydrate constructs can prove advantageous in case of leukemic disorders displaying overabundance of such cells. Copyright © 2017 Elsevier B.V. All rights reserved.

Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

DOEpatents

Stevens, Fred J.

1992-01-01

A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.

Analysis of the flow field generated near an aircraft engine operating in reverse thrust. M.S. Thesis

NASA Technical Reports Server (NTRS)

Ledwith, W. A., Jr.

1972-01-01

A computer solution is developed to the exhaust gas reingestion problem for aircraft operating in the reverse thrust mode on a crosswind-free runway. The computer program determines the location of the inlet flow pattern, whether the exhaust efflux lies within the inlet flow pattern or not, and if so, the approximate time before the reversed flow reaches the engine inlet. The program is written so that the user is free to select discrete runway speeds or to study the entire aircraft deceleration process for both the far field and cross-ingestion problems. While developed with STOL applications in mind, the solution is equally applicable to conventional designs. The inlet and reversed jet flow fields involved in the problem are assumed to be noninteracting. The nacelle model used in determining the inlet flow field is generated using an iterative solution to the Neuman problem from potential flow theory while the reversed jet flow field is adapted using an empirical correlation from the literature. Sample results obtained using the program are included.

Multicompartmental Microcapsules with Orthogonal Programmable Two-Way Sequencing of Hydrophobic and Hydrophilic Cargo Release.

PubMed

Xu, Weinan; Ledin, Petr A; Iatridi, Zacharoula; Tsitsilianis, Constantinos; Tsukruk, Vladimir V

2016-04-11

Multicompartmental responsive microstructures with the capability for the pre-programmed sequential release of multiple target molecules of opposite solubility (hydrophobic and hydrophilic) in a controlled manner have been fabricated. Star block copolymers with dual-responsive blocks (temperature for poly(N-isopropylacrylamide) chains and pH for poly(acrylic acid) and poly(2-vinylpyridine) arms) and unimolecular micellar structures serve as nanocarriers for hydrophobic molecules in the microcapsule shell. The interior of the microcapsule can be loaded with water-soluble hydrophilic macromolecules. For these dual-loaded microcapsules, a programmable and sequential release of hydrophobic and hydrophilic molecules from the shell and core, respectively, can be triggered independently by temperature and pH variations. These stimuli affect the hydrophobicity and chain conformation of the star block copolymers to initiate out-of-shell release (elevated temperature), or change the overall star conformation and interlayer interactions to trigger increased permeability of the shell and out-of-core release (pH). Reversing stimulus order completely alters the release process. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermally conductive of nanofluid from surfactant doped polyaniline nanoparticle and deep eutectic ionic liquid

NASA Astrophysics Data System (ADS)

Siong, Chew Tze; Daik, Rusli; Hamid, Muhammad Azmi Abdul

2014-09-01

Nanofluid is a colloidal suspension of nano-size particles in a fluid. Spherical shape dodecylbenzenesulfonic acid doped polyaniline (DBSA-PANI) nanoparticles were synthesized via reverse micellar polymerization in isooctane with average size of 50 nm- 60 nm. The aim of study is to explore the possibility of using deep eutectic ionic liquid (DES) as a new base fluid in heat transfer application. DES was prepared by heating up choline chloride and urea with stirring. DES based nanofluids containing DBSA-PANI nanoparticles were prepared using two-step method. Thermal conductivity of nanofluids was measured using KD2 Pro Thermal Properties Analyzer. When incorporated with DBSA-PANI nanoparticles, DES with water was found to exhibit a bigger increase in thermal conductivity compared to that of the pure DES. The thermal conductivity of DES with water was increased by 4.67% when incorporated with 0.2 wt% of DBSA-PANI nanoparticles at 50°C. The enhancement in thermal conductivity of DES based nanofluids is possibly related to Brownian motion of nanoparticles as well as micro-convection of base fluids and also interaction between dopants and DES ions.

Effect of dairy powders fortification on yogurt textural and sensorial properties: a review.

PubMed

Karam, Marie Celeste; Gaiani, Claire; Hosri, Chadi; Burgain, Jennifer; Scher, Joël

2013-11-01

Yogurts are important dairy products that have known a rapid market growth over the past few decades. Industrial yogurt manufacture involves different processing steps. Among them, protein fortification of the milk base is elemental. It greatly enhances yogurt nutritional and functional properties and prevents syneresis, an undesirable yogurt textural defect. Protein enrichment can be achieved by either concentration process (evaporation under vacuum and membrane processing: reverse osmosis and/or ultrafiltration) or by addition of dairy ingredients. Traditionally, skim milk powder (SMP) is used to enrich the milk base before fermentation. However, increased quality and availability of other dairy ingredients such as milk protein isolates (MPI), milk protein concentrates (MPC) whey protein isolates (WPI) and concentrates (WPC), micellar casein (MC) and caseinates have promoted their use as alternatives to SMP. Substituting different dry ingredients for skim milk powder in yogurt making affects the yogurt mix protein composition and subsequent textural and sensorial properties. This review focuses on various type of milk protein used for fortification purposes and their influence on these properties.

Slow equilibration of reversed-phase columns for the separation of ionized solutes.

PubMed

Marchand, D H; Williams, L A; Dolan, J W; Snyder, L R

2003-10-10

Reversed-phase columns that have been stored in buffer-free solvents can exhibit pronounced retention-time drift when buffered, low-pH mobile phases are used with ionized solutes. Whereas non-ionized compounds exhibit constant retention times within 20 min of the beginning of mobile phase flow, the retention of ionized compounds can continue to change (by 20% or more) for several hours. If mobile phase pH is changed from low to high and back again, an even longer time may be required before the column reaches equilibration at low pH. The speed of column equilibration for ionized solutes can vary significantly among different reversed-phase columns and is not affected by flow rate.

Flow-induced immobilization of glucose oxidase in nonionic micellar nanogels for glucose sensing.

PubMed

Cardiel, Joshua J; Zhao, Ya; Tonggu, Lige; Wang, Liguo; Chung, Jae-Hyun; Shen, Amy Q

2014-10-21

A simple microfluidic platform was utilized to immobilize glucose oxidase (GOx) in a nonionic micellar scaffold. The immobilization of GOx was verified by using a combination of cryogenic electron microscopy (cryo-EM), scanning electron microscopy (SEM), and ultraviolet spectroscopy (UV) techniques. Chronoamperometric measurements were conducted on nanogel-GOx scaffolds under different glucose concentrations, exhibiting linear amperometric responses. Without impacting the lifetime and denaturation of GOx, the nonionic nanogel provides a favorable microenvironment for GOx in biological media. This flow-induced immobilization method in a nonionic nanogel host matrix opens up new pathways for designing a simple, fast, biocompatible, and cost-effective process to immobilize biomolecules that are averse to ionic environments.

Reverse innovation in maternal health.

PubMed

Firoz, Tabassum; Makanga, Prestige Tatenda; Nathan, Hannah L; Payne, Beth; Magee, Laura A

2017-09-01

Reverse innovation, defined as the flow of ideas from low- to high-income settings, is gaining traction in healthcare. With an increasing focus on value, investing in low-cost but effective and innovative solutions can be of mutual benefit to both high- and low-income countries. Reverse innovation has a role in addressing maternal health challenges in high-income countries by harnessing these innovative solutions for vulnerable populations especially in rural and remote regions. In this paper, we present three examples of 'reverse innovation' for maternal health: a low-cost, easy-to-use blood pressure device (CRADLE), a diagnostic algorithm (mini PIERS) and accompanying mobile app (PIERS on the Move), and a novel method for mapping maternal outcomes (MOM).

Crystal Violet Lactone Salicylaldehyde Hydrazone Zn(II) Complex: a Reversible Photochromic Material both in Solution and in Solid Matrix

PubMed Central

Li, Kai; Li, Yuanyuan; Tao, Jing; Liu, Lu; Wang, Lili; Hou, Hongwei; Tong, Aijun

2015-01-01

Crystal violet lactone (CVL) is a classic halochromic dye which has been widely used as chromogenic reagent in thermochromic and piezochromic systems. In this work, a very first example of CVL-based reversible photochromic compound was developed, which showed distinct color change upon UV-visible light irradiation both in solution and in solid matrix. Moreover, metal complex of CVL salicylaldehyde hydrozone was facilely synthesized, exhibiting reversible photochromic properties with good fatigue resistance. It was served as promising solid material for photo-patterning. PMID:26412101

Analysis of efficiency of waste reverse logistics for recycling.

PubMed

Veiga, Marcelo M

2013-10-01

Brazil is an agricultural country with the highest pesticide consumption in the world. Historically, pesticide packaging has not been disposed of properly. A federal law requires the chemical industry to provide proper waste management for pesticide-related products. A reverse logistics program was implemented, which has been hailed a great success. This program was designed to target large rural communities, where economy of scale can take place. Over the last 10 years, the recovery rate has been very poor in most small rural communities. The objective of this study was to analyze the case of this compulsory reverse logistics program for pesticide packaging under the recent Brazilian Waste Management Policy, which enforces recycling as the main waste management solution. This results of this exploratory research indicate that despite its aggregate success, the reverse logistics program is not efficient for small rural communities. It is not possible to use the same logistic strategy for small and large communities. The results also indicate that recycling might not be the optimal solution, especially in developing countries with unsatisfactory recycling infrastructure and large transportation costs. Postponement and speculation strategies could be applied for improving reverse logistics performance. In most compulsory reverse logistics programs, there is no economical solution. Companies should comply with the law by ranking cost-effective alternatives.

Hyaluronic acid-green tea catechin micellar nanocomplexes: Fail-safe cisplatin nanomedicine for the treatment of ovarian cancer without off-target toxicity.

PubMed

Bae, Ki Hyun; Tan, Susi; Yamashita, Atsushi; Ang, Wei Xia; Gao, Shu Jun; Wang, Shu; Chung, Joo Eun; Kurisawa, Motoichi

2017-12-01

The green tea catechin, (-)-epigallocatechin-3-O-gallate (EGCG), has gained significant attention as a potent adjuvant to enhance the antitumor efficacy of cisplatin while mitigating its harmful side effects. Herein we report the development of a fail-safe cisplatin nanomedicine constructed with hyaluronic acid-EGCG conjugate for ovarian cancer therapy. A simple mixing of this conjugate and cisplatin induces spontaneous self-assembly of micellar nanocomplexes having a spherical core-shell structure. The surface-exposed hyaluronic acid enables efficient delivery of cisplatin into CD44-overexpressing cancer cells via receptor-mediated endocytosis whereas the internally packed EGCG moieties offer an environment favorable for the encapsulation of cisplatin. In addition, the antioxidant effect of EGCG moieties ensures fail-safe protection against off-target organ toxicity originating from cisplatin-evoked oxidative stress. Pharmacokinetic and biodistribution studies reveal the prolonged blood circulation and preferential tumor accumulation of intravenously administered nanocomplexes. Moreover, the nanocomplexes exhibit superior antitumor efficacy over free cisplatin while displaying no toxicity in both a subcutaneous xenograft model and peritoneal metastatic model of human ovarian cancer. Our findings demonstrate proof of concept for the feasibility of green tea catechin-based micellar nanocomplexes as a safe and effective cisplatin nanomedicine for ovarian cancer treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Low frequency sonic waves assisted cloud point extraction of polyhydroxyalkanoate from Cupriavidus necator.

PubMed

Murugesan, Sivananth; Iyyaswami, Regupathi

2017-08-15

Low frequency sonic waves, less than 10kHz were introduced to assist cloud point extraction of polyhydroxyalkanoate from Cupriavidus necator present within the crude broth. Process parameters including surfactant system variables and sonication parameters were studied for their effect on extraction efficiency. Introduction of low frequency sonic waves assists in the dissolution of microbial cell wall by the surfactant micelles and release of cellular content, polyhydroxyalkanoate granules released were encapsulated by the micelle core which was confirmed by crotonic acid assay. In addition, sonic waves resulted in the separation of homogeneous surfactant and broth mixture into two distinct phases, top aqueous phase and polyhydroxyalkanoate enriched bottom surfactant rich phase. Mixed surfactant systems showed higher extraction efficiency compared to that of individual Triton X-100 concentrations, owing to increase in the hydrophobicity of the micellar core and its interaction with polyhydroxyalkanoate. Addition of salts to the mixed surfactant system induces screening of charged surfactant head groups and reduces inter-micellar repulsion, presence of ammonium ions lead to electrostatic repulsion and weaker cation sodium enhances the formation of micellar network. Addition of polyethylene glycol 8000 resulted in increasing interaction with the surfactant tails of the micelle core there by reducing the purity of polyhydroxyalkanoate. Copyright © 2017 Elsevier B.V. All rights reserved.

In vitro evaluation of anticancer nanomedicines based on doxorubicin and amphiphilic Y-shaped copolymers

PubMed Central

Li, Di; Ding, Jian Xun; Tang, Zhao Hui; Sun, Hai; Zhuang, Xiu Li; Xu, Jing Zhe; Chen, Xue Si

2012-01-01

Four monomethoxy poly(ethylene glycol)-poly(L-lactide-co-glycolide)2 (mPEG-P( LA-co-GA)2) copolymers were synthesized by ring-opening polymerization of L-lactide and glycolide with double hydroxyl functionalized mPEG (mPEG-(OH)2) as macroinitiator and stannous octoate as catalyst. The copolymers self-assembled into nanoscale micellar/vesicular aggregations in phosphate buffer at pH 7.4. Doxorubicin (DOX), an anthracycline anticancer drug, was loaded into the micellar/vesicular nanoparticles, yielding micellar/vesicular nanomedicines. The in vitro release behaviors could be adjusted by content of hydrophobic polyester and pH of the release medium. In vitro cell experiments showed that the intracellular DOX release could be adjusted by content of P(LA-co-GA), and the nanomedicines displayed effective proliferation inhibition against Henrietta Lacks’s cells with different culture times. Hemolysis tests indicated that the copolymers were hemocompatible, and the presence of copolymers could reduce the hemolysis ratio of DOX significantly. These results suggested that the novel anticancer nanomedicines based on DOX and amphiphilic Y-shaped copolymers were attractive candidates as tumor tissular and intracellular targeting drug delivery systems in vivo, with enhanced stability during circulation and accelerated drug release at the target sites. PMID:22701317

Combination of micellar casein with calcium and vitamins D2 and K2 improves bone status of ovariectomized mice.

PubMed

Boulier, A; Schwarz, J; Lespesailles, E; Baniel, A; Tomé, D; Blais, A

2016-10-01

Nutritional approaches may help to preserve bone quality. The purpose of our study was to demonstrate the efficiency of an innovative bone health product (BHP) including micellar casein rich in calcium, vitamin D2 and vitamin K2, to improve bone mineral density. The aim of postmenopausal osteoporosis treatment is to decrease bone resorption and/or increase bone formation. Because of the slow bone turnover, osteoporosis prevention and therapies are long-lasting, implying great costs and poor compliance. Even if the effects of nutrition on bone are not as marked as that of pharmaceutical agents, it can be of great help. The purpose of our study was to demonstrate the efficiency of an innovative bone health product (BHP) containing micellar casein rich in calcium, vitamin D2 and vitamin K2, for the improvement of bone mineral density (BMD). An ovariectomized mice model was used to study the effect of different concentrations of the ingredient on BMD and microarchitectural parameters. Blood concentrations of C-terminal telopeptide of type I collagen (CTX), N-terminal propeptide of type 1 procollagene (PINP), alkaline phosphatase (ALP), osteocalcin (OC) and RANKL were also measured to evaluate bone remodelling, To evaluate the efficiency of the product to modulate osteoblast and osteoclast growth and differentiation, primary murine bone cells were used. In vivo studies showed that BMD and microarchitectural parameters were dose-dependently improved after ingestion of the supplement for 3 months. We also report increased osteoblast activity as shown by increased OC activity and decreased osteoclastogenesis as shown by reduced CTX activity. In vitro studies support that BHPs stimulate osteoblast differentiation and mineralization and inhibit osteoclast resorption activity. Our results show that, when chronically ingested, BHPs improve BMD of ovariectomized mice. This work supports that providing an ingredient including micellar casein rich in calcium, vitamin D2 and vitamin K2 is more efficient than the control diet to maintain bone quality.

Insights into intermediate phases of human intestinal fluids visualized by atomic force microscopy and cryo-transmission electron microscopy ex vivo.

PubMed

Müllertz, Anette; Fatouros, Dimitrios G; Smith, James R; Vertzoni, Maria; Reppas, Christos

2012-02-06

The current work aims to study at the ultrastructural level the morphological development of colloidal intermediate phases of human intestinal fluids (HIFs) produced during lipid digestion. HIFs were aspirated near the ligament of Treitz early (30 min), Aspirate(early), and 1 h, Aspirate(1h)(ave,comp), after the administration of a heterogeneous liquid meal into the antrum. The composition of the sample aspirated 1 h after meal administration was similar to the average lumenal composition 1 h after meal administration (Aspirate(1h)(ave,comp)). The colloidal structures of individual aspirates and supernatants of aspirates after ultracentrifugation (micellar phase) were characterized by means of atomic force microscopy (AFM) and cryogenic transmission electron microscopy (Cryo-TEM). AFM revealed domain-like structures in Aspirate(early) and both vesicles and large aggregates Aspirate(1h)(ave,comp). Rough surfaces and domains varying in size were frequently present in the micellar phase of both Aspirate(early) and Aspirate(1h)(ave,comp). Cryo-TEM revealed an abundance of spherical micelles and occasionally presented worm-like micelles coexisting with faceted and less defined vesicles in Aspirate(early) and Aspirate(1h)(ave,comp). In Aspirate(1h)(ave,comp) oil droplets were visualized with bilayers closely located to their surface suggesting lipolytic product phases accumulated on the surface of the oil droplet. In the micellar phase of Aspirate(early), Cryo-TEM revealed the presence of spherical micelles, small vesicles, membrane fragments, oil droplets and plate-like structures. In the micellar phase of Aspirate(1h)(ave,comp) the only difference was the absence of oil droplets. Visualization studies previously performed with biorelevant media revealed structural features with many similarities as presented in the current investigation. The impression of the complexity and diversion of these phases has been reinforced with the excessive variation of structural features visualized ex vivo in the current study offering insights at the ultrastuctural level of intermediate phases which impact drug solubilization.

Inverted micellar intermediates and the transitions between lamellar, cubic, and inverted hexagonal lipid phases. II. Implications for membrane-membrane interactions and membrane fusion.

PubMed Central

Siegel, D P

1986-01-01

Results of a kinetic model of thermotropic L alpha----HII phase transitions are used to predict the types and order-of-magnitude rates of interactions between unilamellar vesicles that can occur by intermediates in the L alpha----HII phase transition. These interactions are: outer monolayer lipid exchange between vesicles; vesicle leakage subsequent to aggregation; and (only in systems with ratios of L alpha and HII phase structural dimensions in a certain range or with unusually large bilayer lateral compressibilities) vesicle fusion with retention of contents. It was previously proposed that inverted micellar structures mediate membrane fusion. These inverted micellar structures are thought to form in all systems with such transitions. However, I show that membrane fusion probably occurs via structures that form from these inverted micellar intermediates, and that fusion should occur in only a sub-set of lipid systems that can adopt the HII phase. For single-component phosphatidylethanolamine (PE) systems with thermotropic L alpha----HII transitions, lipid exchange should be observed starting at temperatures several degrees below TH and at all higher temperatures, where TH is the L alpha----HII transition temperature. At temperatures above TH, the HII phase forms between apposed vesicles, and eventually ruptures them (leakage). In most single-component PE systems, fusion via L alpha----HII transition intermediates should not occur. This is the behavior observed by Bentz, Ellens, Lai, Szoka, et al. in PE vesicle systems. Fusion is likely to occur under circumstances in which multilamellar samples of lipid form the so-called "inverted cubic" or "isotropic" phase. This is as observed in the mono-methyl DOPE system (Ellens, H., J. Bentz, and F. C. Szoka. 1986. Fusion of phosphatidylethanolamine containing liposomes and the mechanism of the L alpha-HII phase transition. Biochemistry. In press.) In lipid systems with L alpha----HII transitions driven by cation binding (e.g., Ca2+-cardiolipin), fusion should be more frequent than in thermotropic systems. PMID:3719075

A study on the inhibitory mechanism for cholesterol absorption by α-cyclodextrin administration

PubMed Central

Furune, Takahiro; Ikuta, Naoko; Ishida, Yoshiyuki; Okamoto, Hinako; Nakata, Daisuke; Terao, Keiji

2014-01-01

Summary Background: Micelle formation of cholesterol with lecithin and bile salts is a key process for intestinal absorption of lipids. Some dietary fibers commonly used to reduce the lipid content in the body are thought to inhibit lipid absorption by binding to bile salts and decreasing the lipid solubility. Amongst these, α-cyclodextrin (α-CD) is reportedly one of the most powerful dietary fibers for decreasing blood cholesterol. However, it is difficult to believe that α-CD directly removes cholesterol because it has a very low affinity for cholesterol and its mechanism of action is less well understood than those of other dietary fibers. To identify this mechanism, we investigated the interaction of α-CD with lecithin and bile salts, which are essential components for the dissolution of cholesterol in the small intestine, and the effect of α-CD on micellar solubility of cholesterol. Results: α-CD was added to Fed-State Simulated Intestinal Fluid (FeSSIF), and precipitation of a white solid was observed. Analytical data showed that the precipitate was a lecithin and α-CD complex with a molar ratio of 1:4 or 1:5. The micellar solubility of cholesterol in the mixture of FeSSIF and α-CD was investigated, and found to decrease through lecithin precipitation caused by the addition of α-CD, in a dose-dependent manner. Furthermore, each of several other water-soluble dietary fibers was added to the FeSSIF, and no precipitate was generated. Conclusion: This study suggests that α-CD decreases the micellar solubility of cholesterol in the lumen of the small intestine via the precipitation of lecithin from bile salt micelles by complex formation with α-CD. It further indicates that the lecithin precipitation effect on the bile salt micelles by α-CD addition clearly differs from addition of other water-soluble dietary fibers. The decrease in micellar cholesterol solubility in the FeSSIF was the strongest with α-CD addition. PMID:25550749

Solution self-assembly and adsorption at the air-water interface of the monorhamnose and dirhamnose rhamnolipids and their mixtures.

PubMed

Chen, M L; Penfold, J; Thomas, R K; Smyth, T J P; Perfumo, A; Marchant, R; Banat, I M; Stevenson, P; Parry, A; Tucker, I; Grillo, I

2010-12-07

The self-assembly in solution and adsorption at the air-water interface, measured by small-angle neutron scattering, SANS, and neutron reflectivity, NR, of the monorhamnose and dirhamnose rhamnolipids (R1, R2) and their mixtures, are discussed. The production of the deuterium-labeled rhamnolipids (required for the NR studies) from a Pseudomonas aeruginosa culture and their separation into the pure R1 and R2 components is described. At the air-water interface, R1 and R2 exhibit Langmuir-like adsorption isotherms, with saturated area/molecule values of about 60 and 75 Å(2), respectively. In R1/R2 mixtures, there is a strong partitioning of R1 to the surface and R2 competes less favorably because of the steric or packing constraints of the larger R2 dirhamnose headgroup. In dilute solution (<20 mM), R1 and R2 form small globular micelles, L(1), with aggregation numbers of about 50 and 30, respectively. At higher solution concentrations, R1 has a predominantly planar structure, L(α) (unilamellar, ULV, or bilamellar, BLV, vesicles) whereas R2 remains globular, with an aggregation number that increases with increasing surfactant concentration. For R1/R2 mixtures, solutions rich in R2 are predominantly micellar whereas solutions rich in R1 have a more planar structure. At an intermediate composition (60 to 80 mol % R1), there are mixed L(α)/L(1) and L(1)/L(α) regions. However, the higher preferred curvature associated with R2 tends to dominate the mixed R1/R2 microstructure and its associated phase behavior.

Structural alterations in lecithin-cholesterol vesicles following interactions with monomeric and micellar bile salts: physical-chemical basis for subselection of biliary lecithin species and aggregative states of biliary lipids during bile formation.

PubMed

Cohen, D E; Angelico, M; Carey, M C

1990-01-01

Using complementary physical-chemical methods including turbidimetry, quasielastic light scattering, gel filtration, and phase analysis, we examined the interactions between dilute concentrations of the common bile salt, taurochenodeoxycholate (TCDC), and uni- and multilamellar vesicles (MLVs) composed of defined molecular species of lecithin (L) and varying contents of cholesterol (Ch). Dissolution rates of MLVs with micellar TCDC, as assessed by turbidimetry, were more rapid with vesicles composed of sn-1 palmitoyl species, typical of biliary L, compared with those composed of the more hydrophobic sn-1 stearoyl species. Incorporation of Ch retarded MLV dissolution rates in proportion to the Ch content, and only at high Ch contents were dissolution rates appreciably influenced by the sn-2 fatty acid composition of L. When MLVs contained Ch in amounts characteristic of intracellular membranes (Ch/L approximately 0.1), the dissolution rates of the individual L species by TCDC accurately predicted the steady state L composition of human bile. TCDC interacted with small unilamellar L/Ch vesicles (SUVs) at concentrations well below, as well as appreciably above, its critical micellar concentration. In accordance with the TCDC-egg yolk L-H2O phase diagram, perimicellar concentrations of TCDC interacted with SUVs to form aggregates that were approximately twice the size of the SUVs. These were consistent with the formation of a dispersed hexagonal (rod-like) phase, which co-existed with aqueous bile salt (BS) monomers and either micellar or unilamellar SUV phases. Micellar TCDC completely solubilized SUVs as mixed micelles, putatively via this transient hexagonal phase. With modest Ch-supersaturation, dissolution was followed by the reemergence of a new vesicle population that coexisted metastably with mixed micelles. With high Ch supersaturation, TCDC extracted L and Ch molecules from SUVs in different proportions to form Ch-supersaturated mixed micelles and Ch-enriched SUVs, in accordance with the metastable phase diagram. These experiments are consistent with the hypothesis that sn-1 palmitoyl L species are subselected for bile, in part, by physical-chemical interactions of intracellular BS concentrations with Ch-poor membranes and that the subsequent evolution of Ch-rich vesicles and Ch-saturated mixed micelles occurs via a transitional hexagonal (rod) phase. These liquid-crystalline states are likely to be transient in Ch-unsaturated biles, but may persist in Ch-supersaturated human biles because of their high Ch contents which retard or inhibit these phase transitions.

Synthesis, X-ray crystallography, spectroscopic characterization and spectroscopic/electrochemical evidence of formation of phenoxy free radical in active center analogs of galactose oxidase - [Cu(Salgly)H₂O] and [Cu(Salphenylalanine)H₂O].

PubMed

Das, Biva; Medhi, Okhil K

2013-03-01

The formation of phenolate free radical is the factor of high turnover for catalytic activity of galactose oxidase (GO) compared to that by inorganic complexes. A new active center analog of GO, [Cu(II)(Salphenylalanine)H(2)O] have been synthesized and its single crystal X-ray analysis was done. In aqueous surfactant micellar solution chemical oxidation as well as electrochemical oxidation of structural models of galactose oxidase - [Cu(II)Salgly·H(2)O] and [Cu(II)(Salphenylalanine)·H(2)O], have been found to generate free radical originating at the phenolate group. Formation of the free radical have been proved by electron paramagnetic resonance spectroscopy, electronic spectroscopy and electrochemistry. Copyright © 2012 Elsevier B.V. All rights reserved.

NMR investigation of the short-chain ionic surfactant-water systems.

PubMed

Popova, M V; Tchernyshev, Y S; Michel, D

2004-02-03

The structure and dynamics of surfactant molecules [CH3(CH2)7COOK] in heavy water solutions were investigated by 1H and 2H NMR. A double-exponential attenuation of the spin-echo amplitude in a Carr-Purcell-Meiboom-Gill experiment was found. We expect correspondence to both bounded and monomeric states. At high concentrations in the NMR self-diffusion measurements also a double-exponential decay of the spin-echo signal versus the square of the dc magnetic gradient was observed. The slow component of the diffusion process is caused by micellar aggregates, while the fast component is the result of the self-diffusion of the monomers through the micelles. The self-diffusion studies indicate that the form of micelles changes with increasing total surfactant concentration. The critical temperature range for self-association is reflected in the 1H transverse relaxation.

Patterned carbon nanotubes fabricated by the combination of microcontact printing and diblock copolymer micelles.

PubMed

Xu, Peng; Ji, Xin; Qi, Junlei; Yang, Hongmin; Zheng, Weitao; Abetz, Volker; Jiang, Shimei; Shen, Jiacong

2010-01-01

A convenient approach to synthesize patterned carbon nanotubes (CNTs) of three morphologies on printed substrates by combination of microcontact printing (microCP) and a plasma-enhanced chemical vapor deposition (PECVD) process is presented. Micelles of polystyrene-block-poly-(2-vinylpyridine) (PS-b-P2VP) in toluene were used as nanoreactors to fabricate FeCl3 in the core domains, and the complex solution was used as an ink to print films with polydimethylsiloxane (PDMS) stamps, different morphologies (porous, dots and stripes patterns) of the FeCl3-loaded micellar films were left onto silicon substrates after printed. After removing the polymer by thermal decomposition, the left iron oxide cluster arrays on the substrate were used as catalysts for the growth of CNTs by the process of PECVD, where the CNTs uniformly distributed on the substrates according to the morphologies of patterned catalysts arrays.

Self-assembly of star micelle into vesicle in solvents of variable quality: the star micelle retains its core-shell nanostructure in the vesicle.

PubMed

Liu, Nijuan; He, Qun; Bu, Weifeng

2015-03-03

Intra- and intermolecular interactions of star polymers in dilute solutions are of fundamental importance for both theoretical interest and hierarchical self-assembly into functional nanostructures. Here, star micelles with a polystyrene corona and a small ionic core bearing platinum(II) complexes have been regarded as a model of star polymers to mimic their intra- and interstar interactions and self-assembled behaviors in solvents of weakening quality. In the chloroform/methanol mixture solvents, the star micelles can self-assemble to form vesicles, in which the star micelles shrink significantly and are homogeneously distributed on the vesicle surface. Unlike the morphological evolution of conventional amphiphiles from micellar to vesicular, during which the amphiphilic molecules are commonly reorganized, the star micelles still retain their core-shell nanostructures in the vesicles and the coronal chains of the star micelle between the ionic cores are fully interpenetrated.

Effect of Hyaluronic Acid on the Self Assembling Behaviour of PEO-PPO Copolymers in Aqueous Solution

NASA Astrophysics Data System (ADS)

Mayol, L.; Borzacchiello, A.; Quaglia, F.; La Rotonda, M. I.; Ambrosio, L.

2008-07-01

The influence of hyaluronic acid (HA) on the self assembling properties of pluronic (PEO-PPO-PEO block copolymers) blends has been studied with the aim of engineering thermosensitive and mucoadhesive polymeric platforms for drug delivery. The gelation temperature (Tgel), viscoelastic properties and mucoadhesive force of the systems were investigated and optimised by means of rheological analyses. Pluronic micellar radius was evaluated by Photon Correlation Spectroscopy (PCS). The addition of Low Molecular Weight HA did not hamper the self assembling process of pluronics just delaying the gelation temperature of few Celsius degrees. Furthermore, HA presence led to a strong increase of the pluronics gel rheological properties. PCS results show, in formulations containing HA, aggregates with hydrodynamic diameters values much higher than those of pluronic micelles. Mucoadhesive experiments indicate the possibility of interactions between the pluronic/HA gel and mucus glycoproteins.

Viscosity and medium effects on the fluorescence and photochemical behaviour of some aryl chalcones

NASA Astrophysics Data System (ADS)

Ebeid, El-Zeiny M.; Abdel-Kader, Mahmood H.; Issa, Raafat M.; El-Daly, Samy A.

1988-05-01

The emission, excitation and absorption spectra toghether with the fluorescence and photochemical quantum yields of some chalcone derivatives have been studied in organic solvents and micellar and microemulsion media. Both 4-[2-(2-pyridyl)ethenyl] ( I) and 4-[2-(4-pyridyl)ethenyl ( II) chalcones show large positive solvatochromic effects. The fluorescence quantum yields increase substantially as the medium viscosity increases with a subsequent decrease in the photochemical quatum yield. Compounds I and II undergo excited-state molecular aggregation in concentrated solutions giving excimer-like emission that coincides with emission from crystalline samples. The enthalpies of photoassociation have been estimated. The chalcone derivative I acts as an efficient quencher of the fluorescence of the laser dye 1,4-bis (β-pyridyl-2-vinyl)benzene via a long-range mechanism. The excited-state lifetimes of both I and II are short and at 20°C their τ values are less than 800 ps.

Model-based analysis of coupled equilibrium-kinetic processes: indirect kinetic studies of thermodynamic parameters using the dynamic data.

PubMed

Emami, Fereshteh; Maeder, Marcel; Abdollahi, Hamid

2015-05-07

Thermodynamic studies of equilibrium chemical reactions linked with kinetic procedures are mostly impossible by traditional approaches. In this work, the new concept of generalized kinetic study of thermodynamic parameters is introduced for dynamic data. The examples of equilibria intertwined with kinetic chemical mechanisms include molecular charge transfer complex formation reactions, pH-dependent degradation of chemical compounds and tautomerization kinetics in micellar solutions. Model-based global analysis with the possibility of calculating and embedding the equilibrium and kinetic parameters into the fitting algorithm has allowed the complete analysis of the complex reaction mechanisms. After the fitting process, the optimal equilibrium and kinetic parameters together with an estimate of their standard deviations have been obtained. This work opens up a promising new avenue for obtaining equilibrium constants through the kinetic data analysis for the kinetic reactions that involve equilibrium processes.